lower extremity arthrology guide

Lower Extremity Arthrology Guide Summer 2015

Derya Anderson Scott Bentley Bow Decker Ashley Haight Cynthia Hobbs Jennifer Rogers Jill Stephenson Andrew Trevino

Table 18

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Arthrology Guide: Table of Contents Introduction to the Pelvic Region………………………………………………………….………..3 Femoroacetabular Joint………………………………………………………………………..…7 Pubic Sympyhsis ………………………………………………………………………….............16 Sacroiliac Joint…………………………………………………………………………………..….20 Introduction to the Knee Complex…………………………………………………………………25 Tibofemoral Joint……………………………………………………………………………......…30 Patellofemoral Joint………………………………………………………………….……...….…37 Introduction to the Ankle Joint………………………………………………………………………42 Proximal Tibiofibular Joint …………………………………………………………...….……45 Distal Tibiofibular Joint ……………………………………………………………….………...47 Talocrural Joint……………………………………………………………………………………...50 Subtalar Joint………………………………………………………………………………………...56 Introduction to the Foot Complex………………………………………………………….………62 Transverse Tarsal Joints ………………………………………………………….…………….65 Distal Intertarsal Joints ………………………………………………………………………….73 Tarsometarsal Joints……………………………………………………..……………………….79 Intermetarsal Joints……………………………………………………………………………….84 Metatarsophalangeal Joints…………………………………………………………………….87 Interphalangeal Joints…………………………………………………………………………….93

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Introduction to the Pelvic Region

The pelvic region contains three major joints. It includes the femoroacetabular joint (hip joint), the sacroiliac joint (SI), and the pubic symphysis. These three joints work together for the purpose of weight bearing, stability, and shock absorption/weight distribution. The joint’s second but equally important purpose is to allow dynamic movement such as walking, running, and jumping. These joints have to be able to work together to provide the stability required so dynamic movements can occur effectively and pain free.

The pelvis is comprised of the sacrum and an innominate bone on each side. The union of these bones creates the sacroiliac joint and the pubic symphysis. As mentioned above, the pelvis serves to distribute weight from the upper body down to the lower extremities. This is done very effectively due to the ring that is created from the joining of these three bones. The pelvis is also important due to the many muscle attachment sites from both the lower extremity and the trunk.

The last component of the pelvic region includes the femur bone. The head of the femur articulates with the acetabulum to create the femoroacetabular joint. The innominate is comprised of three parts: the ilium, the ischium, and the pubis. These three components of the innominate come together to form the acetabulum (Figure 1). It is at this joint that most of the weight bearing occurs.

The pelvic region receives its main blood supply from the internal and external iliac arteries which ultimately originate from the split of the abdominal aorta. The internal iliac artery supplies blood to the organs of the pelvis and the surrounding muscles, and the external iliac artery travels laterally to supply blood to the femoroacetabular joint and the lower extremities. The pelvic region is innervated by the lumbosacral plexus. The plexus arises from the ventral root of T12-‐S4 (Figure 2). The lumbar portion of the plexus goes to innervate the anterior and lateral aspect of the pelvis while the sacral portion innervates the posterior and lateral aspect of the pelvis.

Figure 1. Bones of the acetabulum

Figure 2. Nervous supply of pelvis

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Table 1. Muscles Acting on the Pelvic Joints

Muscle Proximal Attachment Distal Attachment Segmental Innervations

Peripheral Innervations

Gluteus max

Aponeurosis of the erector spinae, sacrum, sacrotuberous ligament & posterior gluteal line (innominate)

Greater trochanter, gluteal tuberosity of the femur & the iliotibial tract

L5-‐S1-‐2 Inferior Gluteal Nerve

Gluteus medius External iliac surface

Oblique ridge on the lateral aspect of the greater trochanter; gluteal aponeurosis

L4-‐5-‐S1 Superior Gluteal Nerve

Gluteus minimis

External iliac surface and margin of the greater sciatic notch

Anterolateral aspect of the greater trochanter

L4-‐5-‐S1 Superior Gluteal Nerve

Piriformis Anterolateral sacrum & posterior inferior iliac spine

Upper border of the greater trochanter (L5) S1-‐2 Nerve to the

piriformis

Superior gemellus

Xternal surface spine of ischium via obturator internus tendon to greater trochanter

Greater trochanter L5-‐S1-‐S2 Sacral Plexus

Obturator internus

Anterolateral wall of the pelvis & obturator membrane

Medial surface of the greater trochanter

L5-‐S1-‐2

Nerve to the obturator internus (from sacral plexus)

Obturator externus

Rami of pubis and ischium; external surface obturator membrane

Trochanteric fossa L3-‐4 Obturator Nerve

Inferior gemellus

Proximal ischial tuberosity via obturator internus tendon

Greater trochanter L4-‐5-‐S1 (S2) Sacral Plexus

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Quadratus femoris Ischial tuberosity Quadrate tubercle of

the femur L4-‐5-‐S1, (S2)

Nerve to quadratus femoris from sacral plexus

Hamstring (Semimembran-‐osus, Semitendinosus, Biceps femoris)

SM: ischial tuberosity ST: ischial tuberosity BF: ischial tuberosity & sacrotuberous lig. (long head) ; lateral lip of linea aspera & lateral supracondylar line (short head)

SM: posterior aspect of the medial tibial condyle ST: proximal, medial tibia BF: the lateral side of fibular head

SM: L4-‐5-S1-‐2 ST: L4-‐5-S1-2 BF: L5-‐S1-2-‐3 to long head; L5-S1-2 to short head

SM: tibial division of the sciatic nerve ST: tibial division of the sciatic nerve BF: tibial branch of sciatic (long head) & fibular branch of sciatic nerve (short head)

Adductor magnus

Inferior pubic ramus, ischial ramus & tuberosity

Gluteal tuberosity, linea aspera, medial supracondylar ridge & adductor tubercle of the femur

L2-‐3-‐4 & L4-‐5-‐S1

Obturator nerve (adductor region) & tibial division of the sciatic nerve

Adductor longus Pubic crest Medial lip of linea

aspera L2, L3, L4 Obturator nerve

Adductor brevis Inferior pubic ramus

Distal 2/3 pectineal line and medial lip linea aspera

L2, L3, L4 Obturator nerve

Adductor minimus Inferior Rami Linea Aspera of the

femur L2, L3, L4 Obturator and Tibial nerve

TFL Anterior superior iliac spine & external lip iliac crest

Iliotibial tract L4, L4, S1 Superior gluteal nerve

Quadriceps (Vastus Lateralis,

VL: intertrochanteric line, greater trochanter, gluteal tuberosity & linea

VL: base & lateral border of the patella VM: medial border

L2, L3, L4 Femoral nerve

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Vastus Medialis, Vastus intermedius)

aspera VM: intertrochanteric line, spiral line, linea aspera & medial supracondylar line VI: anterior aspect of the proximal 2/3rds of the femoral shaft

of the patella VI: lateral border of the patella

Rectus femoris

Anterior inferior Iliac Spine Base of the patella L2, L3, L4 Femoral nerve

Sartorius Anterior Superior Iliac Spine

Medial aspect of the proximal tibia L2-‐L3 (L4) Femoral nerve

Pectineus Superior pubic ramus

Femur between the lesser trochanter & linea aspera (pectineal line)

L2-‐3-‐4 Femoral nerve & obturator nerve

Gracilis Body of the pubis & inferior pubic ramus

Medial surface of tibia, distal to condyle, proximal to insertion of semitendinosus, lateral to insertion of sartorius

L2-‐3-‐4 Obturator nerve

Iliopsoas · Iliacus · Psoas major

Iliacus: iliac fossa, iliac crest, sacral ala & SI ligaments Psoas Major: anterior transverse processes, vertebral bodies & discs

Iliacus: femur just distal to lesser trochanter Psoas: lesser trochanter

Iliacus: (L1) L2-‐3-‐4 Psoas: L1-‐2-‐3-‐4

Iliacus: Lumbar plexus

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Femoroacetabular Joint

The femoroacetabular joint is the articulation of the acetabulum and the head of the femur. The main purpose of the joint is to bear the weight of the trunk and upper extremity in static positions as well as with dynamic movements. The joint must be stable enough to bear the weight of the body as well as mobile enough to allow dynamic movement to occur. Stability is achieved through the many ligaments and muscles surrounding the joint. Mobility is achieved through the nature of the joint being a ball and socket joint. Neurovascular Supply (Figure 3)

The hip joint receives its arterial supply from the medial circumflex artery and the lateral circumflex artery. These two arteries arise from the profunda femoris artery and supply the head and neck of the femur. Specifically, branches off the medial circumflex artery called retinacular arteries are the most abundant and its main supplier. An artery call the ‘artery to the head of the femur’ is located inside the ligamentum teres. It is a branch from the obturator artery and supplies the head of the femur as well but very minimally.

Moore mentions that a nerve innervating any muscles that crosses a joint also innervates the joint itself. This is known as Hilton’s Law. Taking this into account, the hip flexors are innervated by the femoral nerve, lateral rotators by the obturator nerve and the nerve to quadratus femoris, and abductors by superior gluteal nerve. These nerves all originate from the ventral rami of the lumbosacral plexus. Tissue Layers from Superficial to Deep

• Integumentary o epidermis o dermis o hypodermis

• Neurovascular o Nervous Tissue

! Femoral nerve ! Obturator nerve ! Sciatic nerve ! Superior gluteal nerve ! Inferior gluteal nerve

o Vascular Tissue ! Femoral artery ! Medial femoral circumflex artery

Figure 3. Blood supply to the proximal femur

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! Superior and inferior gluteal (minor contributions) ! Lateral femoral circumflex artery ! Artery of ligamentum teres

• Muscle o Hip extensor muscles o Hip adductor muscles o Hip flexor muscles

• Ligaments o Iliofemoral ligament o Ischiofemoral ligament o Pubofemoral ligament

• Joint Capsule/Tissue o Fibrous capsule o Synovial membrane o Synovial fluid

• Articular cartilage • Labrum • Bone

o Head of the femur o Acetabulum

Biomechanics of the Femoroacetabular Joint

The hip joint is a classic ball and socket joint. A ball and socket joint is known to allow the greatest amount of movement. Even so, the number one priority of the hip joint is stability followed by movement. The hip receives its stability from the large amount of muscles and ligaments that surround it. Mobility comes from the three degrees of freedom of the joint. Before discussing the movements in each plane, one must look at the kinematics of the hip. When the femur is moving in a stable pelvis, it is described as femur-‐on-‐pelvis. When the pelvis is moving on a stable femur, it is known as pelvis-‐on-‐femur. Different motions and movements occur depending on which scenario one considers. Below is a description of movements in each plane:

Pelvis-‐on-‐Femur: Sagittal plane: Posterior and anterior tilt Transverse Plane: Internal and external rotation of the hip Frontal Plane: Abduction and adduction of the hip

Femur-‐on-‐Pelvis Sagittal Plane: Flexion and extension Transverse Plane: Internal/external rotation of femur Frontal Plane: Abduction and adduction of hip

Joint Configuration of the Femoroacetabular Joint

As mentioned above, the hip joint is a ball and socket joint. A ball and socket joint is a synovial joint that allows the most amount of freedom as it has movements in all three planes. It consists of a convex surface moving on a concave surface or vice versa. The table below summarizes the osteokinematics, arthrokinematics, and planes the hip joint functions in. The movements are described in open-‐chain position.

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Table 2. Movements of the Femoroacetabular Joint Plane Osteokinematics Arthrokinematics

Sagittal Flexion (120°) Roll anteriorly, glide posteriorly

Sagittal Extension (20°) Rolls posteriorly and glides anteriorly

Transverse Internal Rotation (45°) Rolls medially and glides laterally

Transverse External Rotation (45°) Rolls laterally and glides medially

Frontal Abduction (45°) Rolls laterally and glides medially

Frontal Adduction (30°) Rolls medially and glides laterally

The degrees of motion are according to the AAOS guideline

The roll allows for the joint to move into the proper position while the glide prevents the head of the femur from falling out of the acetabulum. The table below lists the primary and secondary movers of specific motions. Table 3. Joint Motions of the Femoroacetabular Joint

Joint Motion Primary Movers Secondary Movers

Flexion iliopsoas, sartorius, TFL, Rectus femoris, Adductor Longus, pectineus

Adductor Brevis, Gracilis, Gluteus Minimus (anterior fibers)

Extension

Gluteus Maximus, Biceps Femoris (long head), Semitendinosus, Semimembranosus, Adductor Magnus (posterior head)

Gluteus Medius (posterior fibers), Adductor Magnus (anterior head)

Abduction Gluteus Medius, Gluteus Minimus, TFL Piriformis, Sartorius

Adduction Pectineus, Adductor Longus, Gracilis, Adductor Brevis, Adductor Magnus

Biceps Femoris (long head), Gluteus Maximus (lower fibers), Quadratus Femoris

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Internal Rotation N/A

Gluteus Minimus (anterior fibers), Gluteus Medius (anterior fibers), TFL, Adductor Longus, Adductor Brevis, Pectineus

External Rotation

Gluteus Maximus, Piriformis, Obturator Internus, Gemellus Superior, Gemellus Inferior, Quadratus Femoris

Gluteus Medius (posterior fibers), Gluteus Minimus (posterior fibers), Obturator Externus, Sartorius, Biceps Femoris (long head)

Kinetics of the Hip

The forces going through the hip joint vary depending on the activity. In bilateral stance, the hips are in an extended and relatively relaxed position. There are no muscles that are actively working to keep the hips extended. This is due to the fact that the line of gravity is posterior to the hip joint, thereby putting an extension moment on the joint. The ligaments located anterior to the joint (iliofemoral, ischiofemoral, and pubofemoral) tighten up and prevent it from going into hyperextension. In reference to the forces at the hip, there is an equal distribution at both joints. The line of gravity is directed downward going through the center of the pelvis (Figure 4). Since this is an equal distance away from both hip joints, the moment arms are identical, thereby distributing equal compression forces across both joints.

During unilateral stance, the forces at the hip joint change. As one leg is lifted off the ground, the line of gravity does not go through the center of the pelvis anymore, but is shifted towards the stance limb. Because of this shift, the pelvis goes into an adduction moment in relation to the stance limb. In order to keep the pelvis in a neutral position, the hip abductors of the stance limb must generate enough force to counterbalance the adduction torque moment. This puts all of the compression force on the joint, which amounts to approximately 3-‐4 times the body weight. If the hip abductors are incapable of producing enough force to counterbalance the adduction moment of the hip, a trendelenburg gait may occur. One way to compensate for this is a lateral trunk lean towards the stance limb. The moment arm

of the abductors remains the same, but the moment arm of the line of gravity is decreased. This decreases the gravitational pull of the pelvis into an adduction moment, thereby decreasing the amount of counterforce needed from the hip abductors.

Figure 4. Weight vector through the pelvis

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The biomechanics of the hip will also change depending on the amount of coxa vara or coxa valga present. In a normal hip joint, the angle of inclination of the femoral neck is approximately 125°. With coxa vara, the angle of inclination is less than 125°, and in coxa valga, the angle is greater than 125°. In coxa vara, the moment arm for the abductors increases. The abductors have a longer lever arm to work with and can create more torque. However, the abductors are not at their optimal length for force production in this position,

and there is increased torque on the femoral neck. This can result in a fracture. In coxa valga, the moment arm of the abductors decreases, which allows the muscles to be at a more optimal length for force production. This also decreases the torque on the femoral

neck. Since the moment arm is decreased in this position, the abductors must work harder to produce the same amount of force needed to keep the pelvis in a neutral position (Figure 5). Muscular Effects on Kinetics

Muscles play a large role in the biomechanics of the hip. How they influence the hip depends on where they are located in relation to the joint and their line of pull. For this reason, a muscle may be an internal rotator in one position but an external rotator in a different position.

Hip Flexors

The hip flexors are located anterior to the joint. Flexion can occur in a pelvic-‐on-‐femur situation or a femur-‐on-‐pelvic situation. The movement in pelvis-‐on-‐femur is an anterior tilt. A force-‐couple relationship between the back extensors and the hip flexors create the pelvic tilt. The hip flexors rotate around the medial/lateral axis of the hip while the back extensors extend resulting in lumbar lordosis. In a femur-‐on-‐pelvis situation, the muscles contract and the femur is brought up towards the trunk while the abdominal muscles contract to stabilize the pelvis and counter the anterior tilt. The primary and secondary movers of hip flexion can be found in Table 3. Iliopsoas is the major hip flexor and is a combination of two muscles. It’s position along with its cross sectional area makes it a strong hip flexor. Iliopsoas is located to have optimal pull to flex the hip both in an anatomical start position as well as when the hip is flexed to 90°. When the hip is flexed at 90° (as in a sitting position), all other primary hip flexors are insufficient to flex the hip further. Because iliopsoas has many points of origin, and it has a large cross sectional area, it is able to flex the hip past 90° from a sitting position.

Hip Extension The primary hip extensors are gluteus maximus and the hamstrings. Gluteus

maximus has the most hip extension power, due to its large cross sectional area, along with its large moment arm. The optimal position for it to be able to produce the most extension force is starting in the neutral position, and peaks at 70°. Although it is a strong hip extensor, it is activate predominately when it is up against resistance that is greater than the weight of the limb. Unlike gluteus maximus, the hamstrings have a smaller moment arm, and a cross sectional area that is significantly smaller. It is a two-‐joint muscle that consists of three muscle bellies. The hamstrings group differs from gluteus maximus in that

Figure 5. Decreased moment arm due to coxa valga

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its moment arm for extension increases with hip flexion up until 35°, and then decreases thereafter. Once the hip flexes past 90°, the hamstrings contribute very little to hip extension.

Hip Adductors The hip adductors function in three different planes, but they do not adduct within

all planes. As mentioned earlier, the muscle’s line of pull along with joint position will determine the motion at the joint. The hip adductors move in the frontal plane, the sagittal plane, and the transverse plane. In the frontal plane, the adductors adduct the femur.

In the sagittal plane, the adductors act as hip flexors and extensors. Which movement it will elicit is dependent on where the muscle’s line of pull is, relative to the joint axis. For example, when the hip is extended, the line of pull falls anterior to the joint axis, which gives the muscle a flexion moment. When the hip is flexed to approximately 100°, the line of pull falls posterior to the joint axis, and this gives the muscle an extension moment. For this reason, the hip adductors are considered to be one of the primary and secondary movers for hip flexion, and a secondary mover for hip extension.

Hip Abductors Hip abductors are very important, as they are the primary muscles that produce the

counterforce necessary to keep the pelvis in a neutral position during single limb stance. See Table 3 for a list of primary and secondary hip abductors. The primary hip abductors are gluteus medius and gluteus minimis. Along with abducting the femur, they work to stabilize the pelvis a mentioned above in the kinetics section.

Hip External Rotators The primary external rotators are mostly all short muscles and are listed in the table

above in Table 3. These muscles are predominately used in a closed-‐chain position which involves cutting and pivoting. Since the muscles are positioned almost perpendicular to the shaft of the femur, their optimal position to perform external rotation is in the neutral position. When the hip is flexed, obturator internus and the gluteus muscles external moment arm decreases. However, due to the origin and insertion sites of piriformis, hip flexion pass 90° turns piriformis into an internal rotator.

Hip Internal Rotators The hip joint does not have any primary internal rotators. The secondary rotators

are listed in Table 3, which is mainly comprised of the adductors. These muscles have three times the medial rotation torque when the hip is flexed compared to extended. Joint Configuration of the Femoroacetabular Joint

The femoroacetabular joint is synovial ball and socket joint that consists of the union of the head of the femur and the acetabulum. Synovial joints have specific characteristics. The joint usually includes a surrounding joint capsule, a joint cavity with synovial fluid, and articular cartilage covering the bone. The femoroacetabular joint has a thick joint capsule that includes the merging of the iliofemoral ligament, ischiofemoral ligament, and the pubofemoral ligament. The joint also contains synovial membranes that secrete synovial fluid into the joint cavity and act as lubrication. Finally, both the acetabulum and the head of the femur are covered with articular cartilage.

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The lunate surface of acetabulum is covered in hyaline cartilage that creates a horseshoe surface. This is the area that has direct contact with the head of the femur. The transverse acetabular ligament attaches to both ends to complete the circle. Lastly, in order to deepen the acetabulum and to create more surface area, the acetabular labrum spans the entire rim of the socket. It also helps to enhance joint stability by creating a sealing effect, maintaining negative intra-‐capsular pressure. The configuration of the femur also impacts the joint and the type of forces that act upon it. The angle of inclination is the angle between the head of the femur and the neck of

the femur in the frontal plane. Normally, this angle is approximately 125°. When the angle is smaller than 125°, this is known as coxa vara while an angle larger than 125°is known as coxa valga (Figure 6). This angle difference changes the amount of force as well as where the force acts upon the hip (see biomechanics section).

Another angle formed by the head and neck of the femur is the angle of torsion. The normal degree for an

adult is approximately 10°-‐15°. When the angle is smaller, it is called femoral retroversion, and when the angle is larger it is called anteversion. (Figure 7). Changes in this angle also have implications on biomechanics. For example, femoral anteversion may have a negative effect on hip biomechanics by decreasing the joint stability. The head of the femur is more exposed anteriorly and this puts the abductors in a less than optimal position for force production. As mentioned previously, the femoroacetabular joint is known for its ability to provide stability while being able to perform a wide range of motions. The arthrokinematics and osteokinematics of the hip joint allow for this wide variety of movement. This is described in the biomechanics section. Ligaments of the Femoroacetabular Joint

The ligaments of the hip joint are the strongest in the body. This is due to the fact that the hip must be able to support the weight of the body and not dislocate. One of the strongest ligaments of the hip is the iliofemoral ligament, also known as the Y ligament. The Y ligament, along with the other ligaments, spans the entire joint. The thickest areas of the Y ligament are located anterior to the hip to prevent hyperextension of the joint.

Figure 7. Femoral anteversion and retroversion

Figure 6. Femoral angle of inclination

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Table 4. Ligaments of the Femoroacetabular Joint

Along with the ligaments of the hip joint, there are other structures that constrain

the joint. The acetabular labrum increases the surface area that the head of the femur has direct contact with. This increase in surface area helps decrease a possibility of dislocation. The joint capsule is also another structure that constrains the joint and lies under the ligaments. The three main ligaments of the hip joint merge together to help contribute to the joint capsule. The joint capsule covers the head and neck of the femur. It is thickest in the superior anterior portion of the hip and thinnest on the posterior hip. It helps constrain the joint in all directions but is most effective with anterior hip dislocation. Many layers of large muscles also surround the hip. The muscle not moves the hip joint but serves as an extra barrier to contain the hip within the joint. The most muscle bulk around the hip includes the gluteus muscles located on the posterior aspect of the joint. They help prevent a posterior dislocation. Common Pathology of the Femoroacetabular Joint Femoroacetabular Impingement (FAI)

Femoroacetabular Impingement is a problem with the acetabulum and the femoral head not fitting properly. It may lead to reduced range of motion and hip and groin pain. There are two types of FAI: Cam impingement and Pincer Impingement. Cam impingement

Ligament Attachments Function

Iliofemoral Ligament Anterior inferior iliac spine to intertrochanteric line of the femur Prevents hyperextension of hip

Ischiofemoral Ligament

ischium posterior to the acetabulum to greater trochanter & iliofemoral ligament

Helps limit extension of the femur

Pubofemoral Ligament

Iliopubic eminence and superior pubic ramus and merges in with the joint capsule/fibers of iliofemoral ligament

Limits extension and abduction of the hip. Primary role is to prevent over abduction of the hip.

Ligamentum Teres Fovea of the femoral head to acetabular notch and transverse acetabular ligament

When hip flexed 10º, tightens with lateral rotation. Conduit for blood supply to head of femur.

Transverse ligament

Lateral inferior boundary of the acetabular labrum to medial inferior boundary of the acetabular labrum

Completes acetabular labrum rim and prevents inferior displacement of the head of the femur

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involves the abnormal shape of the femoral head, sometimes called a “pistol-‐grip” deformity. The cause is unknown, although some propose that it has to do with a recalcification of the proximal femoral epiphysis. Others suggest that it is from abnormal stresses on the femur. This extra protuberance on the head of the femur does not allow for good clearance of the acetabulum when flexion or abduction occurs at the joint. If this is repeated over long periods of time, wearing of the articular cartilage and labrum may occur. Labral tears and injury usually accompany FAI for this reason. The labrum is innervated, so as a result, the person may experience pain in the hip and groin area.

Pincer impingement occurs when the acetabulum is too large for the femoral head. This can be due to having a deeper acetabular fossa, or the acetabulum being in a retroverted position. When the hip is flexed or abducted, the femoral head may compress surrounding soft tissue or the superior labrum, causing pain in the hip and groin area. If the impingement persists for longer periods of time, the labrum may undergo ossification making the overhang worse. Osteoarthritis (OA)

Osteoarthritis is the most common condition of the hip. It occurs when the articular surfaces of the joint are worn down and there is a rubbing of bone on bone during movements. There are many ways OA can develop. A history of labral tears or CAM impingement will increase the likelihood of developing OA. Jaypee mentions that two predictive factors of developing OA include having previous musculoskeletal injuries and a work history that is physically demanding such as manual labor. It is also mentioned that the two factors related to idiopathic hip OA is aging and weight gain. OA is a degeneration of the cartilage within the joint and it is commonly thought that repetitive weight bearing may contribute to its progression. Jaypee mentions that it is not the repetitive weight bearing but rather the lack of joint forces on the joint that may play a role in developing OA. This is due to the fact that compression on the articular cartilage actually nourishes the joint. Symptoms of hip OA include hip stiffness, anterior groin pain, and decreased range of motion in extension and internal rotation. Fractures of the Pelvis

Hip fractures in older adults are very common and occur at a rate of 98/100,000 people a year. Older adults are at a higher risk for fractures due to their increase in fall risk. Hip fractures can occur for a variety of reasons. As mentioned earlier in the biomechanics section, the hip takes on a compression force of 2-‐3 times the body weight when standing on one limb, which occurs during walking. The femur must be healthy enough to withstad the force on the neck of the femur. Unfortunately, as a person ages, there is a decrease in trabecular density as well as cortical bone mass. This may result in a proximal fracture to the femur. Also, due to the decreased integrity of the bone, a fall could easily cause a fracture. Another factor that may cause a fracture is loss of arterial supply to the head of the femur (avascular necrosis). The head of the femur is mainly supplied by the medial circumflex artery. If there is any trauma to the area that disrupts the blood supply, bone death may occur making it more susceptible to injury.

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The Pubic Symphysis Joint The pubic symphysis (Figure 8) is located

in the anterior midline of the pelvis and consists of the medial articulating surfaces of the right and left pubic bones united by a fibrocartilaginous interpubic disc. In addition to the sacroiliac joint, the pubic symphysis serves as an articulation site of the right and left innominates.

The pubic symphysis is sometimes referred to as the symphysis pubis. This joint is relatively immobile and is classified as a secondary cartilaginous joint. The pubic symphysis functions to resist tension, shearing, and compression of the pelvis during weight bearing activities, such as walking and during childbirth in women.

Research regarding the precise innervation of the pubic symphysis is lacking. However, in a systematic review, Becker et al (2010) found the innervation described as coming from the pudendal and genitofemoral nerves, and branches of the iliohypograstric, ilioinguinal nerves. Becker also found the joint to be supplied by the pubic branch of the obturator artery and branches of the inferior epigastric artery and external pudendal artery. As most fibrocartilaginous tissues depend on diffusion of nutrients from adjacent blood vessels (Neumann 2010), the center of the fibrocartilaginous disc will rely on diffusion from the obturator, inferior epigastric, or external pudendal arteries. Tissue Layers from Superficial to Deep

• Integumentary o Epidermis o Dermis

• Subcutaneous o Fascia o Adipose

• Muscles o Rectus Abdominis o External Oblique o Internal Oblique o Transversus Abdominis o Adductor longus o Adductor Magnus o Adductor Brevis

• Neurovascular o Nervous Tissue

! Iliohypogastric nerve ! Ilioinguinal nerve ! Pudendal nerve ! Genitofemoral nerve

Figure 8. The Pubic Symphysis

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o Vascular Tissue ! Pubic branches of obturator artery ! Inferior epigastric artery ! External pudendal artery

• Ligaments o Superior Pubic Ligament o Arcuate Pubic Ligament o Anterior Pubic Ligament o Posterior Pubic Ligament

• Joint Capsule/Tissue o Hyaline articular cartilage o Fibrocartilaginous disc

• Bone o Pubis bones of the Innominates

Table 5. Joint Motions at the Pubic Symphysis


Superior/Inferior Translation

Rectus abdominis, internal oblique, external oblique, transversus abdominis, adductor longus

N/A

Rotation Rectus abdominis, internal oblique, external oblique, transversus abdominis, adductor longus

N/A

Compression/Traction Rectus abdominis, internal oblique, external oblique, transversus abdominis, adductor longus

N/A

****The muscles listed act indirectly on the relatively rigid pubic symphysis. However, the muscles included in the table reinforce the joint via attachment of the aponeuroses from muscles of the anterior abdominal wall and muscles of the lower extremities to the pubic bones. Biomechanics of the Pubic Symphysis

The pubic symphysis is a relatively immobile cartilaginous joint that is subjected to a variety of forces. For example, during standing activities, the inferior portion of the symphysis is subjected to traction forces while the superior region is subjected to compression forces. The pubic symphysis withstands compression forces with sitting and simultaneous compression and shearing forces during single-‐leg stance (Becker, 2010). The pubic symphysis can experience translation in the sagittal and transverse plane. However, Neumann describes the joint as only having up to 2 mm of translation. Becker et al describe rotation of up to 3° at the pubic symphysis in the frontal and sagittal planes. The pubic symphysis primary function is stabilization and functions to transfer forces from the trunk to the lower extremities. There are no muscles that act as primary movers for the

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stable pubic symphysis. The anterior surface of the adjacent pubic bones serve as an attachment site for the rectus abdominus, internal abdominal oblique, transversus abdominus, and the adductor longus, but these muscles do not directly initiate movement at the pubic symphysis joint. Accessory motions and open/closed pack positions are not experienced at this joint due to the high degree of stability offered by the pubic ligaments. Joint Configuration of the Pubic Symphysis

The articular surfaces of the right and left pubic bones are lined with hyaline cartilage and are joined by the fibrocartilaginous interpubic disc. The surfaces are slight convex in shape, likely designed to resist shearing forces. Due to the relative immobility of the joint, the motion that occurs pubic symphysis is not dependent on the convexity of the articulating surfaces but on the tensile, shear and compressive forces experienced at the joint. Arthokinematic movements of superior or inferior glide of the pubis bones up to 2 mm occur in relation to the forces experienced at the joint. Table 6. Ligaments of the Pubic Symphysis (Figures 9 & 10)

Ligament Attachments Function Associated Constraints

Superior pubic ligament

Lateral pubic crest and pubic tubercle to contralateral lateral pubic crest and tubercle, bridging superior margin of symphysis

Reinforce superior aspect of joint N/A

Arcuate (inferior) pubic ligament

Inferior rami of pubis to contralateral inferior rami of pubis

Reinforce inferior aspect of joint N/A

Anterior pubic ligament

Joins with interpubic disc and aponeurotic expansions of rectus abdominus, transversus abdominus, internal abdominal oblique, and adductor longus

Reinforce anterior aspect of joint

Adductor longs, rectus abdominis aponeurosis, internal oblique aponeurosis, and transversus abdominis aponeurosis

Posterior pubic ligament

Continuous with periosteum of posterior aspect of pubic bones

Reinforce posterior aspect of joint N/A

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Common Pathology of the Pubic Symphysis Osteitis Pubis

Osteitis pubis is a common pathology of the pubic symphysis that results from overuse or shear injuries and subsequent inflammation around the joint. This injury is common among the athlete population. Osteitis pubis often needs to be distinguished between an inguinal hernia and an adductor strain as these injuries present similarly and tend to occur in similar populations. For differential diagnosis purposes, tenderness directly over the pubic symphysis may be the best indicator of osteitis pubis. Symphysis Pubis Dysfunction

Symphysis pubis dysfunction occurs in women during pregnancy. Becker describes how the hormones associated with pregnancy can increase the laxity at the pubic symphysis. Resulting pubic instability can cause pain and difficulty with weight-‐bearing activities and bed mobility for pregnant women. The joint may also be disrupted and widened during childbirth leading to impaired pelvic stability in the postpartum period.

Figure 10: Superior view pubic ligaments

Figure 9: Anterior view of pubic symphysis ligaments

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The Sacroiliac Joint The sacroiliac (SI) joints (Figure 11) mark the transition from the caudal axial

skeleton to the lower appendicular skeleton. The SI joint is located anterior to the posterior superior iliac spine of the ilium. The relatively rigid joint is formed by the articulation between the auricular (ear-‐shaped) surface on the lateral aspect of the sacrum that corresponds with sacral levels S1, S2, S3 (Vleeming 2012) and the auricular surface of the medial aspect of the ilium. Both articulating surfaces are covered with hyaline cartilage. The articular surface of the SI joint has been described as having a boomerang shape with the open angle facing posteriorly (Figure 12).

During early childhood, the SI demonstrates the classical characteristics of a diarthrodial synovial joint with smooth surfaces and considerable mobility. However, over time, between puberty and adulthood the joint transforms from a diarthrodial joint to a modified synarthrodial joint, as explained by Neumann. The articular surfaces become rough and irregular, embedding the subchondral bone within the articular cartilage of the joint order to resist excessive movements between the sacrum and ilium. Several ligaments, some of which are the strongest in the body, reinforce the rigidity of the joint.

The SI joint is primarily designed for stability. The joints transfer loads between the vertebral column and the lower extremities. The SI joints relieve the stress experienced by the pelvic ring secondary to trunk and lower extremity movement and ground reaction forces. Specific innervation of the sacroiliac joint has not been verified in the literature. However, Vleeming (2012) reports dorsal rami L5-‐S3 to be consistently included in various studies of SI joint innervation. Nociceptive axons (C-‐fibers and A-‐delta fibers) have been found in the joint, responsible for pain perception from the SI joint (Vleeming 2012). The posterior division of the internal iliac artery, namely iliolumbar, lateral sacral, and superior gluteal arteries, provide blood supply to the sacroiliac joint. Tissue Layers from Superficial to Deep

• Integumentary o Epidermis o Dermis

Figure 11. Anterior view of SI joint

Figure 12. Boomerang shape of auricular surfaces of ilium and sacrum

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• Subcutaneous o Adipose o Thoracolumbar fascia

! Anterior layer ! Middle layer ! Posterior layer

• Muscles o Latissimus Dorsi o Gluteus Maximus o External Oblique o Internal Oblique o Erector Spinae muscles o Transversus Abdominis o Lumbar Multifidus o Quadratus lumborum o Gluteus Medius o Piriformis o Iliacus (covering anterior SI joint)

• Ligaments o Anterior/Ventral sacroiliac ligament o Posterior Sacroiliac ligament o Interspinous ligament o Sacrotuberous ligament o Sacrospinous ligament o Iliolumbar ligament

• Joint Capsule o Fibrous capsule o Synovial membrane o Synovial fluid o Hyaline cartilage

• Bone o Tuberosity and auricular surface of ilium o Tuberosity and auricular surface of the sacrum

Table 7. Joint Motions at the Sacroiliac Joint


Nutation

(Gravity creates nutation torque), Latissimus dorsi, biceps femoris, rectus abdominus, internal and external oblique, transversus abdominus

N/A

Counternutation Iliopsoas, rectus femoris, erector spinae N/A

Stability Erector spinae, quadratus lumborum, lumbar multifidus, rectus

Muscle activation causes tension in ligaments,

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abdominus, internal oblique, external oblique, transversus abdominus, biceps femoris, gluteus maximus, latissimus dorsi, iliacus, piriformis

compressing surfaces of SI joint

**The muscles listed act indirectly on the relatively rigid SI joint. However, the muscles included in the table reinforce and stabilize the SI joint during dynamic activities such as lifting, running, and carrying via attachments to the thoracolumbar fascia and sacrospinous and sacrotuberous ligaments. Biomechanics of the Sacroiliac Joint

The sacroiliac joint has relatively limited mobility, and unlike most joints in the body, there are no muscles acting directly across the SI joint. The rotational and translational movements that occur at the SI joint are complex. The motions do not occur about a fixed axis, but rather include a combination of parallel and angular movements (Gordon 1991). The motion at the SI joint has best been described as nutation and counternutation, which occur in a near-‐sagittal plane about a near medial-‐lateral axis of rotation that traverses the interosseous ligament. Nutation (sometimes called sacral flexion) refers to an anterior, inferior motion of the sacral promontory and a posterior, superior movement of the sacral apex. Counternutation (sacral extension) is defined as a posterior, superior movement of the sacral promontory and anterior, superior move of the sacral apex. Nutation and counternutation can be described as either sacral-‐on-‐iliac rotation, by iliac-‐on-‐sacral rotation, or by both motions simultaneously (Figure 13). For example, nutation can be described as anterior sacral-‐on-‐iliac rotation or posterior iliac-‐on-‐sacral rotation or anterior sacral rotation with posterior iliac rotation.

Gordon and Alderink describe the role of SI

joint motion in lumbopelvic rhythm during functional activities. During trunk flexion, the lumbar spine moves into flexion, the pelvis anteriorly rotates, and the sacrum follows with nutation or sacral flexion. Upon returning to stand, the sacrum counternutates (extends) as it follows the lumbar spine and pelvis.

The magnitude movement at the SI joint is significantly limited. Translation at the SI joint is limited to 1-‐4 mm and Foley (2006) found the joint motion in the transverse or longitudinal planes does not exceed 2-‐3 degrees. Strong

ligaments surround the joint to limit excessive motion and reinforce the joint’s stability. Slight motion with reinforced stability at the SI joints is vital for attenuating forces between the axial skeleton and the lower extremities.

Figure 13. Nutation and Counternutation of the SI joint

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Joint Configuration of the Sacroiliac Joint The articulation between the sacrum and the ilium contains elevations and

depressions of the articulating surfaces, creating an interlocking mechanism between the two bones. Foley (2006) describes the ilium to have a relative convex surface and the sacrum to have a more concave shape at the SI articulation site. Because the plane of articular surfaces is mostly vertical in orientation, nutation at the SI joint increases compression and consequential stability between the joint surfaces. Therefore, full nutation is considered to be the close-‐packed position of the SI joint. Gravity, ligaments, and activation of surrounding muscles create nutation torque. Load transfer through the pelvic girdle is more effective when the sacrum is in a nutated position. Table 8. Ligaments of the Sacroiliac Joint (Figure 14)


Anterior/Ventral Sacroiliac Ligament

Anterior and inferior borders of the iliac auricular surface to anterolateral sacrum

Resists anterior movement and nutation of the sacral promontory

Posterior/Dorsal Sacroiliac Ligament

Posterolateral border of 3rd and 4th segment of sacrum to lateral ilium near iliac tuberosity and posterior-‐superior iliac spine; thoracolumbar fascia, erector spinae aponeurosis, blends with sacrotuberous ligament to attach to ischial tuberosity

Resists counter-‐nutation of sacrum

Interosseous Ligaments

Fills space that is posterior and superior to joint between lateral sacral crest and iliac tuberosity

Considered most important ligaments directly associated with SI joint; Resists excessive movement

Iliolumbar Ligament Transverse process of L5 to medial iliac crest Restricts sagittal plane movement

Sacrotuberous Ligament

Posterior-‐superior iliac spine, lateral sacrum and coccyx, blends with posterior sacroiliac ligament to attach to ischial tuberosity

Secondary source of stability; restricts nutation

Sacrospinous Ligament

Inferior lateral border of sacrum and coccyx to ischial spine

Secondary source of stability; restricts nutation

An associated constraint to the SI joint is the thoracolumbar fascia, which restricts excessive movement in all directions of motion.

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Common Pathology of the Sacroiliac Joint Low Back Pain

The sacroiliac joints have been found to the source of pain in 15%-‐30% of the population of people who experience chronic low back pain. Pain originating from the SI

joint can refer to multiple areas of the body (Figure 15) including the low back and gluteal region, making SI joint dysfunction difficult to identify and to treat. � SI Dysfunction SI dysfunction and subsequent pain is the result of impaired load transfer through the SI joints. Dysfunction of the joint can be secondary to trauma, leg length discrepancies, excessive lumbar lordosis, joint degeneration, joint stiffness, or displacement such as an upslip or downslip of the joint. The SI dysfunction is also common in women who are pregnant. The hormone relaxin is released in pregnancy, which increases laxity of

the ligaments that support and reinforce joint. A widening effect at the SI joint occurs in preparation for childbirth. However, the excessive motion available at the joint is often a source of pain and aberrant movement patterns for the mother. Also, athletes involved in sports that require frequent unilateral loading of the lower extremities (such as in kicking) are at increased risk for SI dysfunction (Foley). Physical therapists can test for SI dysfunction using a battery of motion palpation tests such as the sacral thrust and Gillet test. Strengthening of surrounding muscles (especially muscles attaching to the thoracolumbar fascia) can help improve the stability of the SI joint and reduce pain related to SI dysfunction.

Figure 14. Posterior ligaments of the SI joint (note: interosseous ligaments are deep to pictured posterior sacroiliac ligament)

Figure 15. SI joint referred pain patterns

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Introduction to the Knee Joint Complex

The knee joint is the largest joint in the body. It is subject to compression and torque during activities such as walking, running, jumping, bending and squatting. Bony articulation at the knee joint complex is relatively unstable and must rely on several muscles and ligaments for structural support (Figure 1). Located in the middle of the chain, the knee is highly impacted by the motions occurring at the hip and ankle joints. Due to it’s location in the chain, and its unstable boney articulation, the knee joint complex is the most frequently injured joint in the body.

The knee joint complex is comprised of two different articulations, the tibiofemoral joint and the patellofemoral joint. These two joints are held within the

joint capsule, forming a synovial hinge joint. Although the proximal aspect of the fibula articulates with the tibia just lateral the knee joint, it is not involved in movement at the knee.

The tibiofemoral and patellofemoral joints work together to allow movement in two planes of motion: flexion and extension in the sagittal plane, and internal and external rotation in the transverse plane. Superior and inferior gliding at the patellofemoral joint are necessary to allow flexion and extension at the tibiofemoral joint. During extension, the patella functions to increase force produced by the quadriceps femoris. Various pathologies or lack of proper functioning of the joints and associated structures can lead to impairments and decreased participation. Neurovascular Supply

Much of the knee joint is highly vascularized with the exception of a portion of the meniscus. The main blood supply comes from branches of the femoral artery which then becomes the popliteal artery. A large genicular anastomosis is responsible to supply blood to majority of the knee structures and surrounding muscles. However, the exception is the inner portion of the menisci. These avascular sections then have inhibited tissue healing after an injury to the inner portion of the lateral or medial meniscus. The femoral artery passes down the posterior aspect of the thigh and transitions into the popliteal artery to supply the hamstring, gastrocnemius, soleus, and plantaris musculature. This artery runs most anterior in the joint before splitting into

Figure 1. The knee

Figure 2. Anastomosis around the knee

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the anterior and posterior tibial arteries at the distal aspect of the joint capsule. The capsule and ligaments of the knee joint are supplied by five collateral branches originating from the popliteal artery. These branches form the genicular anastomosis (Figure 2) which surrounds the knee joint and provides adequate blood supply. The branches include the superior medial and lateral geniculars, the inferior medial and lateral geniculars, and the middle genicular artery. In the case that the popliteal artery is obstructed, such as in a long duration of knee extension, the anastomotic branches will continue to provide sufficient blood supply to the knee. Venous return is transported by the posterior tibial vein, which transitions into the popliteal vein in the popliteal fossa. The popliteal vein traverses the knee joint alongside the popliteal artery before becoming the femoral vein. The small saphenous vein is also a tributary into the popliteal vein and transports blood from the posterior aspect of the

malleolus superiorly into the popliteal fossa. The knee and surrounding muscle innervations can be

broken up into four different compartments supplied by separate nerves: anterior, posterior, medial and lateral (Figure 3). The anterior aspect of the knee and thigh muscles are innervated through the femoral nerve while muscles of the posterior and lateral aspects receive innervation from branches of the sciatic nerve known as the common fibular branch and the tibial branch respectively. The medial aspect is innervated via the obturator nerve with cutaneous innervation from the saphenous cutaneous nerve. The posterior aspect of the knee, the popliteal fossa, is the point where the sciatic nerve splits into the tibial division and the common fibular division (Figure 4). The tibial nerve supplies

muscles found posterior to the knee joint such as the soleus, gastrocnemius, plantaris, and popliteus. The common fibular nerve runs on the lateral aspect of the joint, following the medial aspect of the biceps femoris, and wraps closely around the neck of the fibular where it is subject to injury. The common fibular nerve supplies the short head of the biceps femoris. The posterior cutaneous nerve of the thigh provides innervation to the skin posterior to the knee joint.

Figure 3. Nerve supply

Figure 4. Popliteal fossa structures

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Table 1. Muscles Acting on the Tibiofemoral and Patellofemoral Joints (Figure 5 & 6)

Muscle Proximal Attachment Distal Attachment Segmental

Innervation Peripheral Innervation

Anterior Region

Rectus femoris

Anterior inferior iliac spine and ilium superior to acetabulum

Vastus lateralis Greater trochanter and lateral lip of linea aspera of femur

Vastus medialis Intertrochanteric line and medial lip of linea aspera of femur

Vastus intermedius

Anterior and lateral surfaces of shaft of femur

Quadriceps tendon and attachments to base of patella forming patellar ligament to tibial tuberosity; medial and lateral vasti also attach tibia and patella via patellar retinacula


Articularis Genu Distal anterior shaft of femur

Proximal portion of synovial membrane of the knee


Medial Region

Sartorius

Anterior superior iliac spine and superior part of notch inferior to it

Superior portion of medial surface of tibia L2, L3 Femoral

nerve

Gracilis Body and inferior ramus of pubis

Superior portion of medial surface of tibia L2, L3 Obturator

nerve Lateral Region

Tensor fascia latae

Anterior superior iliac spine and external lip of iliac crest

Iliotibial tract L4, L5, S1 Superior gluteal nerve

Posterior region

Semitendinosus Medial surface of superior part of tibia

Semimembrano-‐sus

Ischial tuberosity Posterior part of medial condyle of tibia

L5, S1, S2 Tibial division of sciatic nerve

Biceps femoris: Long head Short head

Long head: Ischial tuberosity Short head: linea aspera and lateral supracondylar line of femur

Lateral side of head of fibula L5, S1, S2

Long head: Tibial division of sciatic nerve Short head: Common fibular division of sciatic nerve

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Tissue Layers from Superficial to Deep (Figure 7)

• Skin o Epidermis o Dermis

• Adipose • Fascia

o Fascia Latae ! Iliotibial tract ! Intermuscular septa

o Patellar retinaculum, medial and lateral • Muscles and tendons

o Anteriorly ! Quadriceps tendon ! Patellar tendon ! Articularis Genu

o Medially ! Semitendinosus ! Semimembranosus ! Sartorius ! Gracilis

o Posteriorly ! Gastrocnemius ! Plantaris ! Popliteus

o Laterally ! Biceps femoris

• Bursa o Anteriorly

! Suprapatellar ! Prepatellar ! Infrapatellar

o Medially ! Anserine ! Semimembranosus

o Laterally ! Subtendinosus of biceps femoris ! Bursa deep to Iliotibial tract

• Neurovasculature

Gastrocnemius Lateral head: lateral aspect of lateral condyle of femur Medial head: popliteal surface of femur superior to medial condyle

Posterior surface of calcaneus via Achilles tendon

Plantaris

Inferior end of lateral supracondylar line of femur, oblique popliteal ligament

Posterior surface of calcaneus via Achilles tendon

S1, S2

Tibial Nerve

Figure 7. Sagittal cut of the knee

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o Common fibular nerve o Tibial nerve o Sural nerve o Popliteal artery

! Superior medial genicular artery ! Superior lateral genicular artery ! Middle genicular artery ! Inferior medial genicular artery ! Inferior lateral genicular artery

• Extracapsular ligaments o Anterolateral ligament o Lateral collateral ligament o Medial collateral ligament

• Joint Capsule • Intracapsular ligaments

o Posterior cruciate ligament o Anterior cruciate ligament

• Menisci: medial and lateral • Articular cartilage of femur • Articular cartilage of tibia • Bones

o Patella o Tibia o Femur

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The Tibiofemoral Joint

The tibiofemoral joint is the largest of the knee joint complex and produces most of the movement at the knee. This joint undergoes a great deal of impact during daily activities. Function at the tibiofemoral joint is vital for shock absorption in closed-‐chain activities such as walking, running, squatting, and jumping.

The tibiofemoral joint and its associated structures are surrounded by a thin layer of fibrous connective tissue called the joint capsule. This capsule is lined with an extensive, thick synovial membrane and

synovial fluid, giving the joint its classification as the largest synovial joint in the body. The synovial fluid allows for very low friction within this mobile joint. Deep to the joint capsule are as many as 14 bursae (Figure 8). These are found at areas producing high friction with movement where tissues articulate.

The tibiofemoral articulation forms a hinge joint with the distal femur and the proximal aspect of the tibia. The distal end of the femur includes two major projections known as the medial and lateral femoral condyles. The intercondylar notch separates the joint into the medial and lateral compartments. The medial condyle is positioned more anteriorly and has a larger articulation with thicker articular cartilage, while the lateral condyle is bigger in shape. These large, asymmetrical condyles articulate with the relatively flat and shallow medial and lateral tibial condyles. This creates an incongruent articulation at the joint that is mechanically weak and lacks overall structural stability. Therefore, the surrounding muscles and ligaments are crucial for providing stabilization at the joint.

Unlike other structures in the lower extremity, these surfaces are highly unstable in effort to allow a large range of motion to occur at the joint. Due to the incongruent surfaces, much of the stability and strength of the knee is provided less by bony articulation and is instead provided by the numerous ligamentous structures and the muscles and tendons acting at the joint. The knee joint reaches its greatest stability in a position of full extension with slight external rotation. This point of maximal contact and congruency is the close-‐packed position. In this position, the ligaments are in full tension, and range of motion is limited in all directions. In order for motion to occur at the joint, the knee must be in some degree of flexion. The joint will reach its greatest amount of motion in 25 degrees of flexion, the most non-‐congruent position, known as loose-‐packed. With movement into flexion, the joint will rely on ligaments and tendons to provide joint stability. Increasing muscle strength also provides increased stability and decreased likeliness of injury. In order to achieve maximal articulation at this incongruent joint, small fibrocartilaginous structures, the menisci, are attached to the articular surfaces between the femoral and tibial condyles (Figure 9). With forces at the tibiofemoral joint that are 2-‐4 times the amount of body weight, the menisci function to add depth to this shallow

Figure 8. Tibiofemoral joint

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articulation. The menisci increase the surface area, shock absorption, and stability, while decreasing friction. These structures also function to provide proprioception at the joint and assist with accessory motion. The lateral meniscus is O-‐shaped. It has less surface area, does not have a strong attachment to the tibia, and has fewer attaching structures than the medial meniscus. The C-‐shaped medial meniscus attaches to the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and the semimembranosus. With stronger attachments to the tibial plateau, it is less movable within the joint, placing it at higher risk for injury. Table 2. Joint Motions of the Tibiofemoral Joint Joint Motion Primary Movers Secondary Movers

Knee flexion

Hamstring muscles: Semimembranosus Semitendinosus, Long head of biceps femoris

Sartorius Gracilis Popliteus Gastrocnemius Plantaris

Knee extension

Quadriceps femoris: Rectus femoris Vastus lateralis Vastus intermedius, Vastus medialis

Tensor fascia latae assists in maintaining knee extension

Internal rotation

Semimembranosus Semitendinosus with knee flexed; Popliteus in non-‐weight bearing activity with knee extended

Gracilis, Sartorius Popliteus (in non-‐weight bearing)

External rotation

Biceps femoris: short & long head when knee is flexed Popliteus (in weight bearing)

Biomechanics of the Tibiofemoral Joint The tibiofemoral joint is a shallow, hinge joint with two degrees of freedom. The primary motions are flexion and extension, with some rotational movement occurring in knee flexion (Figure 10). The surrounding tendons and ligaments restrict these motions.

Muscles are referred to as two main groups acting at this joint: the knee

Figure 9. Menisci of the knee

Figure 10. Motions of the knee

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extensors and the knee flexor-‐rotators. The quadriceps femoris muscles are solely responsible for extension at the knee. They are able to produce a powerful extensor moment at the joint due to their line of pull around the patella and large cross sectional area. The hamstring muscles are antagonists to the extensors and are the primary flexors at the joint.

Typically, the knee allows for 140 degrees of passive flexion, limited by soft tissue structures, and 0 to 10 degrees of hyperextension, limited by bony articulation or activation of the hamstring muscles. During a walking gait cycle, 75 degrees of knee flexion and 0 degrees of knee extension are necessary for typical ambulation. Rotational movement is also possible but is more limited. External rotation reaches 45 degrees of passive range of motion while internal rotation is typically 30 degrees. For ambulation, 10 degrees of both external and internal rotation are required.

A rotational component is essential for terminal knee extension and stability. During the last 30 degrees of extension, the tibia externally rotates 6 to 30 degrees under the femur in an open-‐chain position or the femur internally rotates over the tibia in close-‐chain movements in order to accomplish what is known as the “screw home” mechanism. This is a conjunct movement at the tibiofemoral joint with simultaneous extension and rotation providing increased stability. This articulation allows the least amount of movement, creating the close-‐packed position. To return to a flexed position, the popliteus provides the slight internal rotation necessary to “unlock” the knee.

The tibiofemoral joint focuses on movements of the femur on the tibia, as this joint functions primarily in weight bearing, closed-‐chain activities. Due to its mid-‐position in the lower extremity, the knee is highly affected by the joint mechanics and forces occurring at both the foot and the knee. The bony alignment of these structures impacts the positioning of the knee, referred to as the Q-‐angle (Figure 11). This is measured by forming a line from anterior superior iliac spine (ASIS) to middle of the patella and a line extending to the tibial tuberosity. Females typically have a greater Q-‐angle with normal range 15-‐17 degrees while males typically have 10-‐14 degrees. An angle greater than 17 degrees is referred to as “knock-‐knee” or excessive genu valgum and a small or negative Q-‐angle is called “bow-‐leg” or genu varum. During weight bearing, this angle can greatly impact the musculature line of pull and pressures at the knee joint, lead to possible pain or injury. Joint Configuration of the Tibiofemoral Joint

The tibiofemoral joint has two degrees of freedom; movement occurs in the sagittal and the transverse plane. The majority of the motion at the tibiofemoral joint occurs as flexion and extension in a sagittal plane about a mediolateral axis. When the knee is flexed, movement also occurs as internal and external rotation in the transverse plane about a longitudinal axis about the tibiofemoral joint.

Figure 11. Q-angle

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The arthrokinematic movement at the tibiofemoral joint is dependent on the position of the joint and whether it is in a closed-‐chain position (weight bearing) or open chain (non-‐weight bearing). During a closed-‐chain event, such as the stance phase of gait, the convex surface of the distal femur moves about the stationary, concave surface of the tibial condyles. In order to maintain the congruency of the joint, the femoral condyles rotate anteriorly while simultaneously gliding posteriorly on the tibia (Figure 12). However, during open chain position in the swing phase of gait, the concave surface of the tibial condyles moves relative to the convex surface of the femoral condyles. In this scenario, the articulation of the joint is maintained by rotation and glide of the tibial condyles both in the anterior direction (Figure 13).

The arthrokinematic motion for axial rotation is different. This motion is only available when the knee is in a flexed position, and is maximal at 90 degrees of knee flexion. Here, a spin movement occurs in the transverse plane about a longitudinal axis at the tibiofemoral joint. In a loaded position, each single point on the femoral condyles rotates around a single point on the meniscal surface of the tibial condyles. These menisci are able to deform slightly to accommodate the spin while remaining in place due to stabilization from the popliteus and semimembranosus.

Figure 12. Tibiofemoral motion

Figure 13. Convex/Concave rules

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Table 3. Ligaments of the Tibiofemoral Joint (Figure 14) Ligament Attachments Function Associated Constraints

Fibrous capsule of the knee

Extensive attachments from margins of femoral condyles to margins of the tibial condyles

Thickenings that communicate with the suprapatellar bursa

Assists to prevent friction

Tibial/medial collateral (MCL)

Medial epicondyle of the femur to medial condyle and shaft of tibia

Stabilize medial aspect of joint (mainly in extension)

Prevents abduction of the tibia/ genu valgus, lateral rotation, and anterior displacement of the tibia on the femur

Fibular/lateral collateral (LCL)

Lateral epicondyle of femur to the head of the fibula

Stabilizes lateral aspect of the joint

Prevents adduction of the tibia/ genu varus and lateral rotation of the tibia

Anterior cruciate (ACL) Anteromedial bundle Posterolateral bundle

Medial part of anterior intercondylar area of the tibia to the posterior portion of the medial surface of the lateral condyle of the femur

Prevents posterior displacement of the femur on the tibia Taut in flexion The larger of the bundles, taut in extension

Prevents hyperextension of knee, medial tibial rotation, and limits anterior translation of tibia on femur Limits knee flexion Limits extension

Posterior cruciate (PCL) Anterolateral bundle Posteromedial bundle

From the posterior intercondylar area of the tibia to the lateral surface of the medial condyle of the femur

Prevents anterior displacement of the femur on the tibia Taut in flexion (most at 80-‐90 degrees) Taut in extension

Prevents hyperflexion of the knee, medial tibial rotation, and limits posterior translation of tibia on femur

Menisci: Medial Lateral

Anterior and posterior regions of the intercondylar area of the tibia and fibrous capsule at the medial collateral ligament Anterior and posterior regions of the intercondylar area of the tibia

Increase joint depth and articulation, provide stability, decrease friction, increase shock absorption at the joint

Assist with accessory motion

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Common Pathology of the Tibiofemoral Joint Meniscal Injuries The medial and lateral menisci are under a large amount of load at the knee joint and are susceptible to injury. Injuries can occur during forced rotation or in conjunct with other ligamentous injuries such as ACL or MCL tears. The medial meniscus is often injured with forced external rotation, while the lateral meniscus is often injured during internal rotation. Many times the patient may hear an audible “pop”, feel instability or locking at the joint, and have acute swelling that develops slowly. Treatment of a torn meniscus depends on the section that was damaged (Figure 15). The outer portion is known as the red-‐red zone and has a good blood supply for healing. A tear in this region can be managed conservatively. The middle portion, referred to as the red-‐white zone, has some blood flow and may or may not fully heal with conservative treatment. The inner portion is referred to as the white-‐white zone, due to its lack of blood supply. This portion is not able to heal on its own and requires surgical repair or removal. Medial Collateral Ligament (MCL) Injuries to the medial collateral ligament (MCL) occur with high impact forces to the lateral aspect of the knee, thus forcing it into a valgus position. The MCL can also be injured through rotational, non-‐contact forces. A force to the knee in full extension may create a combination injury of the MCL, joint capsule, and tendons attaching at the pes anserine while a force at 20 to 30 degrees of knee flexion will produce an isolated injury to the MCL. Generally, MCL injuries are managed with conservative treatment including a period of minimal range of motion or immobilization. Due to its good blood supply, surgical repair is rarely used as treatment.

Figure 14. Ligaments of the knee

Figure 15. Meniscal zones

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Lateral Collateral Ligament (LCL) A lateral collateral ligament (LCL) injury is almost always a combination injury involving the cruciate ligaments, joint capsule and possible fibular nerve injury. An isolated LCL injury is rare. Often, injury occurs with a high velocity force to the medial aspect of the knee causing a varus stress at the joint. This may happen with or without internal rotation of the tibia. An injury sustained to the LCL will most often require surgical repair due to poor blood supply in the area. Anterior Cruciate Ligament (ACL) An injury to the anterior cruciate ligament (ACL) is very common and generally occurs within a sports population. Females are at a much higher risk to sustain an ACL tear than males, often due to anatomical differences such as a wider Q-‐angle. The mechanism of injury can be due to contact, non-‐contact with rotational forces, or hyperextension. The ACL can be injured by itself or as an “unhappy triad” along with the joint capsule, lateral meniscus (or medial) and MCL. The initial event will often produce an audible “pop” and immediate swelling. Partial ACL tears are also possible but are often treated the same as a complete tear. Surgical repair is the standard protocol but is not necessary in all cases depending on the patient’s activity level and functional ability. Posterior Cruciate Ligament (PCL) The posterior cruciate ligament (PCL) is rarely injured. It is much wider than the anterior cruciate ligament and is one of the strongest ligaments in the entire body. The PCL is at its most vulnerable position at 90 degrees of knee flexion. The most common mechanism of injury is referred to as a dashboard injury, occurring during a motor vehicle accident where the tibia contacts the dashboard and is forced posteriorly. The PCL may also be injured with a “fall on bent knee”, hyperextension, or a rotational force. The signs and symptoms of a PCL tear are less noticeable as the patient may not remember the injury occurring, may or may not feel a pop in the back of the knee, and will have minimal swelling. Management is generally conservative, with a more severe degree of injury requiring a knee brace. Surgery is rarely performed to repair the posterior cruciate ligament. Osteoarthritis Osteoarthritis is a common condition at the knee joint and occurs as a result of degenerative changes over time. This condition is often present in people over the age of 50 but can be seen in younger individuals. Osteoarthritis presents with varying levels of stiffness, limited range of motion, crepitus, and can become very painful as the articular cartilage in the joint is worn away overtime. This condition has a higher rate of occurrence in people who have a prior medical history of a total menisectomy procedure. Osteoarthritis can be managed conservatively through weight loss, medication, activity modification, cortisone injections, or by wearing a brace. However, once the osteoarthritis becomes severely debilitating, the standard treatment is either a joint resurfacing or a total knee replacement surgery. This procedure replaces part or all of the joint in order to decrease pain with activity. The surgery is generally very effective but may also wear out overtime and often people will not regain full range of motion or strength after the procedure.

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Patellofemoral Joint

The patellofemoral joint, which is located within the joint capsule, is the articulation between the patella, and the femur. Stabilization of this joint is provided by the joint capsule, medial and lateral reticular fibers, quadriceps femoris muscle, and the boney alignment of the joint itself. The patella is classified as a sesamoid bone, as it is embedded within the patellar tendon. The patella functions to protect the anterior surface of the knee joint and also to increase the mechanical advantage of the quadriceps. Table 4. Joint Motions at the Patellofemoral Joint

Joint motion Primary Movers Secondary Movers

Superior Glide Occurs during knee extension

Quadriceps femoris -‐Rectus femoris -‐Vastus lateralis -‐Vastus medialis -‐Vastus intermedialis

N/A

Inferior Glide Occurs during knee flexion

Lengthening of quadriceps femoris, passive elongation or eccentric activation

Hamstrings flex the knee, and inferior glide occurs

Biomechanics of the Patellofemoral Joint Function of the Patella for Mechanical Advantage

The knee extension torque is the force generated by the quadriceps femoris multiplied by the internal moment arm (Figure 16). The knee extensor internal moment

arm is the distance between the medial-‐lateral axis of rotation at the knee, and the line of pull of the quadriceps femoris muscles. The patella functions to increase the mechanical advantage of the quadriceps femoris muscle group for knee extension by increasing the internal moment arm. The knee extensor moment arm is the greatest between 20 and 60

degrees of knee flexion, and the maximal knee extension torque is in a similar arch of motion, between 30 and 75 degrees of knee flexion. In addition to length of internal moment arm, internal torque is influenced by line of pull of muscle as well as muscle length.

Figure 16. Internal moment arm of the femur

Figure 17. Compressive forces on the patella

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Compression at the Patellofemoral Joint

The patella functions to distribute compressive forces on the femur from the pull of the quadriceps femoris muscle group by increasing the contact area between the femur and patellar tendon. The patellofemoral joint is subject to large amounts of compression force (Figure 17), as the patella is compressed into the intercondylar groove of the femur by the pull of the quadriceps femoris during everyday activity such as walking, stair climbing, and running. During level walking, the compression on the patellofemoral joint is 1.3 times body weight. During stair climbing, the compression force is 3.3 times body weight, and during running the compression force can raise to up to 7 times body weight.

Compression force at the patellofemoral joint is determined by force generated by quadriceps femoris, and the knee flexion angle. During a closed chain squat, the compression force is greatest between 60 and 90 degrees of knee flexion. In this range, the force generated by the quadriceps femoris is the greatest, and the horizontal force component into the patella is the greatest.

Throughout the same range of motion that the compression force on the patellofemoral joint is the largest, the contact area between the patella and intercondylar groove of the femur is also the largest. The larger contact surface through this range functions to protect the joint from excessive stress, as stress = force/contact area. Path of the Patella on the Femur

Optimal tracking of the patella on the femur is considered to be movement of the articular surfaces with the greatest amount of surface area and the least amount of stress. This section will discuss the factors that contribute to optimal patellar tracking. During knee extension, the patella tracks superiorly and laterally over the femur in the intercondylar groove as it is pulled by the quadriceps femoris. The lateral tracking of the patella is due in part to the larger pull of the vastus lateralis relative to vastus medialis, and also due to boney alignment. Excessive lateral tracking of the patella is associated with the occurrence of patellofemoral pain, as well as patella subluxation. The Q-‐Angle is a clinical measurement intended to quantify the lateral muscle pull on the patella. The Q-‐Angle (Figure 18) is the angle between the line from the anterior superior iliac spine on the pelvis to the midpoint of the patella (representing the line of force of the quadriceps) and the line connecting the tibial tuberosity and the midpoint of patella (representing the longitudinal axis of patellar tendon). The larger the angle, the larger the lateral pull on the patella. Q-‐Angle values for typical alignment are 10-‐14 degrees for males, and 15-‐17 degrees for females. It is important to consider the limitations of the Q-‐Angle measurement, such that it is only a static measurement, and that it has a poor association with pathology at the patellofemoral joint.

While the boney alignment and increased relative pull by vastus lateralis muscle pull the patella laterally, there are several mechanisms that restrict lateral movement. The lateral facet of the intercondylar groove is steeper than the medial facet, which works

Figure 18. The Q-angle

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to prevent the patella from shifting too far laterally. The oblique fibers of vastus lateralis work to counteract the lateral pull from the vastus lateralis. Additionally, the medial patellar retinaculum, which attaches to the medial patella, femur, tibia, medial meniscus, and deep side of vastus medialis, restricts excessive lateral shift of the patella. Joint Configuration of the Patellofemoral Joint

The patellofemoral joint is an arthrodial (planar joint) joint. It is a non-‐axial joint but has several accessory motions, including superior and inferior glides in the frontal plane, medial and lateral translation, tilt in the transverse plane, and spin in the frontal plane. Tilt and spin of the patellofemoral joint are difficult to study, as there is wide variation in motion among individuals. Superior and inferior glide, and medial and lateral translation will be discussed below.

Boney articulation

The intricate contours of the boney articulation between the femur and the patella guide the accessory motion that occurs at the patellofemoral joint. The distal end of the femur encompasses the medial and lateral condyles, which fuse to form the intercondylar groove on the anterior surface of the femur. Within this groove, the patella tracks as it is pulled by the force of the quadriceps femoris muscle group. As mentioned in the biomechanics section, the lateral facet of the intercondylar groove is steeper than the medial facet, and this functions to prevent excessive lateral displacement of the patella. The patella has a posterior surface that was built for articulation, as it is covered in approximately 5mm of articular cartilage, which functions to disperse large compressive forces across the joint. On the articular surface runs a convex vertical ridge, which sits between the medial and lateral facets of the intercondylar groove of the femur. Its anterior surface is convex. The shape of the patella is somewhat like a triangle, with the apex located inferiorly, and the base located superiorly. Superior/Inferior Glide

During knee flexion, the patella moves inferiorly on the femur in the intercondylar groove, and during knee extension, the patella moves superiorly on the femur. At full knee flexion, the patella contacts the femur at its superior pole, and lies below the intercondylar groove. As the patella moves superiorly during the arch of motion into full extension, the contact point between the patella and femur moves from the superior pole of the patella to the inferior pole of the patella, with the greatest contact occurring in the range of 60-‐90 degrees of knee flexion. Through this range, the patella moves within the intercondylar groove, and this is considered the closed packed position of the patellofemoral joint, as the patella and femur

Figure 19. Gliding of the patella

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are in greatest congruency. In the last 20 degrees of the arch of motion into full extension, the patella moves superior to the intercondylar groove to rest on top of the suprapatellar fat pad at full extension. Full knee extension is the open pack position of the patellofemoral joint, as the patella is located superior to the intercondylar groove, and is least stable in this position. Medial and Lateral Patellar Translation

Medial and lateral shifts, or translations, occur during flexion and extension of the knee, but to a lesser extent than the superior and inferior glide that occurs. Nha et al (2007) observed that during a lunge, the patella shifted medially 2.8mm by 30 degrees of flexion, and then shifted laterally 2mm by 90 degrees of flexion.

During open chain motion, when the tibia moves on the femur during flexion and extension, the patella glides in the stationary intercondylar groove of the femur. During closed chain motion, the intercondylar groove of the femur glides on the stationary patella. Table 5. Ligaments of the Patellofemoral Joint (Figure 20)


Patellar Ligament Inferior pole of patella to tibial tuberosity

Transmission of forces from quadriceps femoris tendon across patella to tibia

Resists excessive superior glide of patella during knee extension

Medial Patellofemoral Ligament (medial patellar retinacular fibers)

Medial epicondyle of femur to medial boarder of patella

Resists lateral displacement of patella

N/A

Lateral Patellofemoral Ligament (lateral patellar retinacular fibers)

Lateral epicondyle of femur to lateral boarder of patella

Resists medial displacement of patella

N/A

Iliotibial tract Tensor fascia latae to fibular head

Resists medial displacement of patella

N/A

Common Pathology of the Patellofemoral Joint Patellofemoral Pain Syndrome

Patellofemoral Pain Syndrome (PFPS), which is defined as pain, inflammation, and instability of the extensor mechanism of the knee from stress, is a common pathology, with a 1 in 4 incidence in the general public. The area of pain varies, and is common on any boarder of the patella, and on the retro-‐patellar surface. While the specific physiological cause of the pain is not always well understood, there are several risk factors associated with PFPS. These factors include large Q-‐Angle, internal rotation of the femur, patellar hypermobility/hypomobility, pronated foot posture, decreased strength of the hip

Figure 20. Ligaments of the

patellofemoral joint

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abductors, hip extensors, hip external rotators, and decreased flexibility of the quadriceps, hamstrings, gastrocnemius, and iliotibial tract. Patellar Tendinopathy

Patellar Tendinopathy is an overuse injury with inflammation of the patellar tendon that often results from increased running or jumping activities. The site of pain is most common at the inferior pole of the patella but can occur at other points along the tendon. This pathology often presents with decreased quadriceps flexibility, pain to palpation of the tendon, and pain during knee extension. Three stages of tendinopathy include stage one, during which pain occurs only after physical activity. In stage two, pain occurs during and after activity. Stage three consists of almost constant pain that is debilitating. Activity modification is crucial for recovery. Patellar Subluxation/Dislocation

A patellar subluxation describes a situation in which the patella comes partially out of place but goes back into place. Patellar dislocation describes a situation in which the patella moves completely out of place and does not move back into place naturally. Ninety-‐five percent of displacements are lateral translations, and in many cases the medial patellar retinaculum and the medial patellofemoral ligament are damaged during the displacement, and in some situations the patella fractures. Displacements occur most often when the knee joint is at 20-‐30 degrees of flexion. Predisposing factors for patellar subluxation or dislocation include patellar hypermobility, a flattened articular surface of the patella, a shallow intercondylar groove on the femur, a large Q-‐Angle, tibial torsion, and faulty movement patterns. Patellar Bursitis

A bursitis is defined as inflammation and swelling of a bursa. The bursas relevant to the patellofemoral joint include the prepatellar, suprapatellar, and the infrapatellar bursa. (Picture!) Bursitis can occur as a result of acute trauma, overuse mechanisms such as repetitive compression, or infections. Patellar bursitis often presents with swelling and limited range of motion, and normally heals with conservative management such as activity modification and modalities for pain and swelling. Osgood-‐Schlatter’s Disease and Sinding-‐Larsen-‐Johansson Syndrome

An apophysis is a secondary ossification center on a bone at the insertion point for a tendon. It is common for the apophysis to become inflamed with overuse in young, skeletally immature, athletes, and this pathology is called an apophysitis. An apophysitis occurring at the tibial tuberosity is named Osgood-‐Schlatter’s Disease, and at the inferior pole of the patella it is named Sinding-‐Larsen-‐Johansson Syndrome. Apophysitis can heal with rest and activity modification, as well as correction of muscular imbalances.

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Introduction to the Ankle Region

The ankle (Figure 1) consists of the talocrural joint, the proximal and distal tibiofibular joints, and in some respects the subtalar joint as well. These joints provide both stability and an ability to influence surrounding structures, allowing for the complex mechanics and force transmissions of gait to occur efficiently. The stability can be observed in the sturdy, mortise-‐like structure of the talocrural joint, the extensive ligamentous and tendinous support of the region, and the single degree of freedom about which the motions of plantar flexion and dorsiflexion occur. The ankle’s capacity to influence nearby structures can be observed by the communication through the lower leg via the syndesmosis to the proximal tibiofibular joint, as well as the frontal plane motion of the calcaneus on the talus via the subtalar joint, which occurs with the talus remaining relatively stationary within the tight-‐fitting talocrural joint.

The ankle joints receive blood from branches of the popliteal artery, the posterior tibial artery, the fibular artery and the anterior tibial artery. Blood supply to specific joints will be discussed later in this section. Nerve supply to the joints comes from the common fibular nerve, the deep fibular nerve, and the tibial nerve. The tissue layers of the ankle joints have many components in common with a few structures unique to specific joints such as the retinaculum in the distal joints. Tissue layers for each joint will be discussed later in this section. Table 1. Muscles Acting on the Ankle The musculature in the lower limb is often broken into compartments, an anterior compartment, lateral compartment, superficial posterior compartment and a deep posterior compartment (Figure 2). In the table below are the muscles in the compartments, the attachments and the innervations.

Figure 1. The ankle

Figure 2. Compartments of the leg

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Muscle Proximal Attachments

Distal Attachments

Segmental Innervations

Peripheral Innervations

Anterior Compartment Muscles Extensor digitorum longus

From the lateral tibial condyle, proximal 3/4th of the fibula and interosseous membrane

To the dorsal digital expansions of toes 2-‐5

L4-‐L5-‐S1

Deep fibular (fibular) nerve

Extensor hallucis longus

From the middle 1/2 of the fibular surface & interosseous membrane

To the distal phalangeal base of the great toe

L4-‐L5-‐S1

Deep fibular nerve

Fibularis tertius

From the distal fibula and interosseous membrane

To the base of the 5th metatarsal

L4-‐L5-‐S1

Deep fibular nerve

Tibialis anterior

From the lateral condyle and superior half of the lateral surface of the tibia & interosseous membrane

To the medial cuneiform & base of 1st metatarsal

L4-‐L5-‐S1

Deep fibular nerve

Lateral Compartment Muscles Fibularis longus

From the head & proximal 2/3rds of the fibula

To the lateral aspects of the 1st metatarsal & adjacent medial cuneiform

L5-‐S1 and sometimes L4

Superficial fibular nerve

Fibularis brevis

From the distal 2/3rds of the fibula

To the lateral base of the 5th metatarsal

L5-‐S1 and sometimes L4

Superficial fibular nerve

Superficial Posterior Compartment Muscles Gastrocnemius From the posterior

aspect of the femoral condyles and joint capsule

To the posterior calcaneal surface S1-‐2 Tibial nerve

Plantaris From the lateral supracondylar line

To the posterior calcaneal surface

L5-‐S1-‐S2 Tibial nerve

Soleus From the posterior aspect of the head & proximal 1/4th of the fibula & tibial soleal line

To the posterior calcaneal surface L5-‐S1-‐2 Tibial nerve

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Deep Posterior Compartment Muscles Flexor digitorum longus

From the posterior tibia distal to the soleal line

To the plantar surfaces of the distal phalangeal bases


Flexor hallucis longus

From the distal 2/3rds of the posterior fibular surface & interosseous membrane

To the plantar aspect of the distal phalangeal base of the 1st toe


Tibialis posterior

From the interosseous membrane, lateral tibial surface & medial fibular surface

To the navicular, intermediate cuneiform and bases of metatarsals 2-‐4

L4-‐L5-‐S1 Tibial nerve

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The Proximal Tibiofibular Joint (PTFJ) The PTFJ joint (Figure 3) is considered part of the ankle joint despite its close relation to the knee joint as it has no effect on knee motion but is involved in motion of the ankle. The PTFJ is classified as a plane joint formed by the head of the fibula and the lateral condyle of the tibia. No osteokinematic motion occurs at the PTFJ but the joint surfaces glide superiorly and inferiorly on one another, influencing and responding to the distal tibiofibular joint. This relationship between the proximal and distal tibiofibular joints in due to the connection they share to the interosseous membrane. Since gliding motions are not taken into consideration, this joint has 0 degrees of freedom. However, the PTFJ is essential for ankle movement and can disrupt motion if injury to this region occurs. The blood supply to the PTFJ comes from the inferior lateral genicular artery branching off of the popliteal artery and the anterior tibial recurrent artery branching off of the anterior

tibial artery. Nerve supply to this joint comes from branches of the common fibular nerve as well as branches from the nerve to the popliteus muscle. Tissue Layers from Superficial to Deep

• Integumentary o Epidermis o Dermis o Hypodermis

• Superficial fascia • Subcutaneous tissue

o Superficial neurovascular supply o Loose connective tissue

• Tendons and sheaths o Biceps femoris tendon o Popliteus tendon

• Joint capsule • Neurovascular supply

o Lateral genicular artery and anterior tibial recurrent artery o Common fibular nerve and branches of the nerve to the popliteus

• Ligaments o Lateral collateral ligament o Anterior tibiofibular o Posterior tibiofibular

• Bones o Fibular head of the fibula o Proximal lateral surface of the tibia

Figure 3. The PTFJ

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Table 2. Joint Motions at the PTFJ Joint motion Primary Movers Secondary Movers No true motion

occurs at this joint N/A N/A

Table 3. Ligaments of the PTFJ

Ligament Attachments Function Associated Constraints Anterior tibiofibular ligament

From the anterior lateral surface of the tibia to the anterior medial surface of the fibula

Stabilizes the PTFJ Resists anterior movement of the fibular head

Posterior tibiofibular ligament

From the posterior lateral surface of the tibia to the posterior medial surface of the fibula

Stabilizes the PTFJ Resists posterior movement of the fibular head

Interosseous ligament From interosseous border of the tibia to the interosseous border of the fibula

Stabilizes the PTFJ and DTFJ and helps disperse load during weight bearing activities

Resists separation of the tibia and fibula

Common Pathology of the PTFJ The PTFJ is rarely injured in isolation and normally occurs secondarily to other injuries. Disruption and pain the PTFJ is common after a high ankle sprain, which will be discussed in the next section.

According to Milankov et al in 2013, dislocation of the fibular head is rare and tends to occur with twisting motions when the knee is bent and planted. Milankov et al discuss the importance of ruling out dislocation when seeing a patient complaining of knee pain as it can often go unnoticed. Morrison et al in 2011 found that after traumatic fibular dislocations or other injuries to the knee, the fibular head is likely to have some instability due to laxity in the ligaments. Morrison found that surgery was an effective means of stabilizing the joint for proper function. Due to the location of the common fibular nerve wrapping around the fibular head, after a fracture or trauma to the fibular head, sensory information to the lateral aspect of the lower leg and foot may be compromised (Figure 4).

Figure 4. Common fibular nerve injury

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The Distal Tibiofibular Joint (DTFJ) The DTFJ (Figure 5) is unique since it is a fibrous syndesmosis joint, not a synovial joint, and does not have a joint capsule. This joint relies on the interosseous membrane and ligamentous attachments for stability. Little motion occurs at this joint and its main function is to keep the tibia and fibula approximated to form a stable mortise for the talus to function in for movement. It is a stiff joint with 0 degrees of freedom but still allows for some separation during certain movements like dorsiflexion when the talus must wedge in between the tibia and fibula. This wedging makes for the most stable position of the ankle allowing for push off during gait. The blood supply to the DTFJ comes from the posterior medial malleolar branch of the fibular artery and branches of the anterior and posterior tibial arteries. Nerve supply to this joint comes from the tibial nerve and deep fibular nerve. Tissue Layers from Superficial to Deep




• Bursa o Subcutaneous bursa of the

lateral malleolus • Retinaculum (Figure 6)

o Superior extensor retinaculum o Superior and inferior fibular

retinacula • Tendons and sheaths

o Fibularis longus tendon o Fibularis brevis tendon o Fibularis tertius tendon o Extensor digitorum longus tendon

• No joint capsule present • Neurovascular supply

o Posterior medial malleolar branch and anterior and posterior tibial arteries o Deep fibular nerve and tibial nerve

• Ligaments

Figure 5. DTFJ

Figure 6. Retinacula of the lateral ankle

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o Anterior tibiofibular o Posterior tibiofibular

• Bones o Distal fibula (lateral malleolus) o Distal lateral surface of the tibia

• Interosseous membrane Table 4. Joint Motions at the DTFJ Joint motion Primary Movers Secondary Movers No true motion

occurs at this joint N/A N/A

Biomechanics of the Proximal and Distal Tibiofibular Joints The main function of both the proximal and distal tibiofibular joints is to participate in the mild spreading of the mortise at maximal dorsiflexion. These two joints are intimately connected in function due to the shared interosseous membrane, and as a result will be discussed together. During dorsiflexion, the mortise spreads to accommodate the larger, anterior portion of the talus. The fibula translates superiorly to allow this. The proximal tibiofibular joint (PTFJ), a synovial joint, has joint surfaces that are mostly flat and covered with articular cartilage. In response to ankle dorsiflexion, the fibular joint surface will glide superiorly. The PTFJ occurs between the head of the fibula and the posterolateral aspect of the lateral condyle of the tibia and has anterior and posterior ligaments for stability, which resist motion of the joints in the anterior/posterior direction and allows slight motion in

the superior/inferior direction. There are also connections of the PTFJ with the muscular and ligamentous structures of the knee, such as the popliteus tendon, which stabilizes the joint as it crosses it posteriorly. The biceps femoris and lateral collateral ligament of the knee must transmit forces from the fibula to the tibia across the PTFJ, which is another reason why this joint must be relatively stable.

Moving distally, the DTFJ is a syndesmosis formed by the articulation of the medial surface of the distal fibula and the fibular notch of the tibia. This joint is classified as a fibrous, synarthrodial joint as the interosseous membrane closely binds it. The interosseous ligament and the anterior and posterior tibiofibular ligaments enhance this stable union.

These ligaments strongly resist motion of the tibia and fibula in the anterior/posterior directions, while allowing some movement in the superior/inferior directions. This mirrors the motions that are

allowed/restricted at the PTFJ. As a result, the fibula slides superiorly during dorsiflexion, which allows for spreading of the mortise. By spreading this small motion across two firm joints, the necessity for mobility with significant stability is well balanced.

The interosseous membrane also plays a key role in this mechanism (Figure 7). As the fibula translates superiorly during dorsiflexion, the interosseous membrane keeps the fibula fixed to

Figure 7. Relationship of tibia and fibula to the interosseous membrane

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the tibia and also prevents excessive superior translation of the fibula, which also maintains the integrity of the PTFJ and DTFJ.

Table 5. Ligaments of the DTFJ


Anterior tibiofibular ligament

Flat band between margins on the anterior surface of the tibia and fibula

Stabilize DTFJ Resists movement of fibula on tibia

Posterior tibiofibular ligament

From the posterior surface of the tibia to the posterior surface of the fibula

Stabilize DTFJ Resists movement of fibula on tibia

Interosseous ligament From interosseous

border of the tibia to the interosseous border of the fibula

Stabilizes the PTFJ and DTFJ and helps disperse load during weight bearing activities

Resists separation of the tibia and fibula

Common Pathology of the DTFJ Norkus and Floyd in 2001 discussed the etiology of syndesmotic ankle sprains or “high ankle sprains” being a result of the talus forcing the tibia and fibula apart most often during hyperdorsiflexion and external rotation. This force can damage the ligaments or the interosseous membrane in the process (Figure 8). While syndesmotic ankle sprains are less common than other ankle sprains, they often have a longer period of recovery and are more difficult to detect in examination. Walsh and DiGiovanni in 2004 studied fractures of the distal fibula often sustained during a lateral ankle sprain and found many of these fractures were at risk for nonunion due to changes in gait pattern and lack of diagnosis.

Figure 8. High ankle sprain injury

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The Talocrural Joint

The talocrural joint (Figure 9) includes to the articulation between the distal tibia and fibula proximally and the body of the talus distally. It is a synovial joint with a joint capsule and associated ligaments for structural stability. The motions about this hinge joint are primarily dorsiflexion and plantar flexion (Figure 10). The blood supply to the talocrural joint comes from the anterior and posterior tibial arteries and the malleolar branches of the fibular artery. The nerve supply to the talocrural comes from tibial nerve and the deep fibular nerve.

Tissue Layers from Superficial to Deep • Integumentary

o Epidermis o Dermis o Hypodermis



• Bursa o Subcutaneous bursa of the medial malleolus o Subcutaneous bursa of the lateral malleolus

• Retinaculum o Superior extensor retinaculum o Inferior extensor retinaculum

• Tendons and sheaths o Anterior

! Fibularis tertius tendon ! Extensor digitorum longus tendon ! Extensor hallucis longus tendon ! Tibialis anterior tendon

o Medial ! Tibialis posterior tendon ! Flexor digitorum longus tendon ! Flexor hallucis longus tendon

o Posterior ! Calcaneal tendon

• Joint capsule

Figure 9. The talocrural joint

Figure 10. Dorsiflexion and plantarflexion

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• Neurovascular supply o Anterior and posterior tibial arteries and the fibular artery o Deep fibular nerve and tibial nerve

• Ligaments o Medial

! Deltoid ligament o Lateral

! Posterior talofibular ! Calcaneofibular ! Anterior talofibular

• Bones o Distal fibula (lateral malleolus) o Distal tibia (medial malleolus) o Talus

Table 6. Joint Motions at the Talocrural Joint


Dorsiflexion of the ankle

Tibialis anterior Extensor digitorum longus, Extensor hallucis longus, Fibularis tertius

Plantarflexion of the ankle

Gastrocnemius, Soleus Fibularis longus, Fibularis brevis, Flexor digitorum longus, Flexor hallucis longus, Plantaris, Tibialis posterior

* Inversion and eversion are negligible at the talocrural joint and will be discussed with the subtalar joint

Biomechanics of the Talocrural Joint

The talocrural joint is a synovial, hinge type joint with a fibrous capsule as well as ligamentous structures for further stability. It is a critical structure for ambulation and must be stable enough to effectively transmit forces from the foot to the leg while still allowing sufficient range of motion for sagittal plane motions. As a result, the talocrural joint has a variety of factors that increase its stability while maintaining sagittal mobility.

The talocrural joint is often described as resembling a mortise (Figure 11), with the medial and lateral malleoli minimizing the frontal plane motions of inversion and eversion of the talus, while maximizing the sagittal plane motions of plantar flexion and dorsiflexion. Unlike the rigid mortise of a carpenter, however, the talocrural joint is afforded greater functionality due to its Figure 11. Bones of the

talocrural joint

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ability to adjust via the mobility of the proximal and distal tibiofibular joints. The body of the talus articulates with the mortise at three surfaces, which share a

continuous layer of articular cartilage. There is a large (fibular) facet laterally, a smaller medial (tibial) facet, and a dome-‐shaped (convex) trochlear facet on the superior aspect. Since the size and orientation of the lateral and medial facets of the talocrural joint are asymmetrical, the distal fibula moving on the larger lateral facet must undergo a greater displacement than the medial malleolus of the tibia during the motions of dorsiflexion and plantar flexion (Figure 12). This is achieved by superior and inferior motion of the fibula at both the proximal and distal tibiofibular joints.

The concave articular surface created by the distal tibia and fibula and the superior articular surface of the talus allow for the sagittal plane motions of plantar flexion and dorsiflexion. The anterior portion of the trochlear facet of the talus is wider than the posterior surface, necessitating a spreading of the distal tibia and fibula to accommodate the motion of dorsiflexion. When the talocrural joint is in maximal dorsiflexion, it is considered to be most stable since it in its closed pack orientation. During dorsiflexion in open chain, the talus must glide posteriorly and roll anteriorly. This is clinically

relevant in the event that a patient is lacking dorsiflexion ROM, which would indicate that mobilizations in the anterior to posterior direction would facilitate the desired motion.

It is critical that the tibia and fibula be able to spread to allow dorsiflexion to occur, but it is also critical that these bones maintain a certain degree of congruence so that the ankle mortise can maintain its hold on the talus. The interosseous membrane and distal tibiofibular ligaments stabilize the separation. In very high amplitude forced dorsiflexion events the interosseous membrane can be disrupted, resulting in a syndesmotic sprain (See pathology of the DTFJ).

Conversely, the talocrural joint is much less stable in plantar flexion, 10° of plantar flexion being the open packed position of the joint. In plantar flexion, the talus must glide anteriorly and rolls posteriorly. This reduces the approximation of the talus in the mortise of the tibia and fibula since the narrower (posterior) portion of the talus is now articulating with the mortise of the ankle. This instability coupled with the increased stability of the inferior lateral malleolus preventing eversion has implications clinically as there is a much greater occurrence of ankle sprains in the plantar-‐flexed, inverted position (See pathology of the talocrural joint.)

Another unique feature of the talocrural joint is its oblique axis of rotation. Since the lateral malleolus sits slightly inferior and posterior to the medial malleolus, the axis of rotation passing through the body of the talus and the tips of both malleoli sits at an angle. The axis deviates from purely mediolateral by approximately 10-‐25° in the frontal plane and 6-‐15° in the horizontal plane (Figure 13). This creates a unique set of motions about the talocrural joint, influencing motions of supination and pronation in the foot. The motion

Figure 12. Facets of the talus

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of dorsiflexion occurs in conjunction with slight abduction and eversion of the foot, and plantar flexion in conjunction with slight adduction and inversion. This being said, it should be noted that the primary motions about the talocrural axis is plantar flexion and dorsiflexion, with the eversion and inversion components being much more prominent at the subtalar joint.

The necessary range of motion for functional gait is 10° of dorsiflexion and 20° of plantar flexion. During gait, there is eccentrically controlled plantar flexion immediately after the foot makes contact with the ground and the foot must be controlled. The muscle bellies of the muscles that create plantar flexion of the ankle are located on the posterior aspect of the lower leg and knee and insert either on the calcaneus or more distally on the foot. The primary movers for ankle plantar flexion are the gastrocnemius muscle, which has a proximal attachment at the posterior aspect of the femoral condyles, and soleus muscle, which has a proximal attachment on the proximal fibula and tibia (as noted on muscle table). These two muscles have a common distal attachment of the posterior calcaneus, affording them an optimal line of pull into plantar flexion. They also have a large cross sectional area, necessary for the strong concentric contraction in the push-‐off phase of gait. In push-‐off, the plantar flexion of the ankle must propel the leg off the ground and forward into swing phase.

Other muscles that assist in plantar flexion are the plantaris, tibialis posterior, fibularis longus and brevis, flexor digitorum longus and flexor hallucis longus muscles. However, these muscles have a less direct line of pull and a smaller cross sectional area as compared to the gastrocnemius and soleus muscles and for that reason are not considered primary movers of the ankle into plantar flexion. During plantar flexion, the anterior capsule and anterior talofibular ligament (ATFL) become taught, providing resistance to excessive motion. The achilles tendon, which attaches the soleus and gastrocnemius muscle bellies to the calcaneus, is broad and thick to accommodate the large forces required for the push off phase of gait and also to provide passive resistance to dorsiflexion. Other structures, such as the calcaneofibular ligament, have similar passive tensioning properties.

For dorsiflexion to occur in open chain, the convex talus must glide posteriorly and roll anteriorly in the concave mortise of the ankle. As a result, any structure that becomes taut during posterior translation of the talus will provide passive tension against dorsiflexion, creating an additional degree of stability to the position of dorsiflexion. This includes the gastrocnemius and soleus muscles and the achilles tendon.

Dorsiflexion is achieved by primarily the tibialis anterior muscle, and is assisted by the extensor digitorum longus and extensor hallucis longus muscles. The greatest degree of dorsiflexion occurs during stance phase of gait, where the concave mortise of the tibia and fibula must move anteriorly over a stabilized, convex talus in a closed chain fashion. In this orientation, the mortise must both glide and roll anteriorly. At the maximum point of

Figure 13. Axis of rotation of the talocrural joint

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dorsiflexion, stability is key in order to accept compressive forces during the push off phase of gait, which can amount to over four times body weight. Table 7. Ligaments of the Talocrural Joint


Medial Ligaments of the Ankle Posterior tibiotalar (Deltoid ligament)

From medial malleolus to medial tubercle of talus

Anterior tibiotalar (Deltoid ligament)

From medial malleolus to medial talar surface

Tibiocalcaneal (Deltoid ligament)

From medial malleolus to sustentaculum tali

Tibionavicular (Deltoid ligament)

From medial malleolus to navicular tuberosity and plantar calcaneonavicular ligament

Stabilizes joint & limits talar abduction

Resists eversion of the ankle

Lateral Ligaments of the Ankle Posterior talofibular From lateral malleolus

to the posterior tubercle of the talus

Calcaneofibular From lateral malleolus to tubercle of lateral calcaneus

Anterior talofibular From lateral malleolus to posterior tubercle of the talus

Stabilize joint & limits talar adduction

Resists inversion of the ankle

Common Pathology of the Talocrural Joint Inversion Ankle Sprains

The anterior talofibular ligament (ATFL) is the most frequently injured ligament in the body. When fibers of a ligament of the ankle are torn it is known as an ankle sprain. The ATFL is usually the first of the lateral ankle ligaments to be injured during forcible inversion of the plantar flexed, weight bearing foot (Figure 14). Sprains of the ankle are almost always in the inversion direction, due to the strong, broad deltoid ligament on the medial side of the ankle coupled with the distally projecting lateral malleolus, which both limit eversion. The joint is also more vulnerable in plantar flexion, which is the open

Figure 14. Inversion ankle sprain

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packed position and allows for more mobility and less stability. Other lateral ligaments involved in inversion sprains are the calcaneofibular ligament

(CFL) and the posterior talofibular ligament (PTFL). The ATFL may tear completely, resulting in chronic instability of the ankle joint. In severe sprains, the CFL is also torn, followed by the PTFL. Inversion ankle sprains have a high incidence in sports that require running and jumping. They often result from landing from a jump onto another player’s foot, resulting in rolling into inversion. Basketball is particularly notorious for ankle sprains, with 70-‐80% of players having had at least one ankle sprain. This is clinically significant because patients who have a history of ankle sprains have an increased likelihood of subsequent sprains, according to Smith and Reischel in 1986, as well as long lasting strength and balance deficits according to Lin et al in 2010.

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The Subtalar Joint The subtalar joint refers to the articulation between the talus and the calcaneus. There are three articulations between these two bones, allowing for the triplanar motions of supination and pronation. Since there is appreciable side-‐to-‐side and rotary motion at this joint, the foot is able to move independent of the ankle or leg. This allows the weight bearing subtalar joint to act as a buffer for rotational forces transmitted by the body weight while keeping the foot stabilized on the ground, and makes it possible to perform functional tasks such as walking on uneven terrain, balancing, quickly changing directions, or standing with feet wide apart. Blood supply to the subtalar joint comes from the posterior tibial artery and fibular arteries. The posterior tibial nerve, the medial plantar nerve, and the sural nerves give nerve supply to the subtalar joint. Tissue Layers from Superficial to Deep




• Bursa o Subcutaneous calcaneal burse

• Retinaculum o Flexor retinaculum o Inferior extensor retinaculum

• Tendons and sheaths o Anterior

! Fibularis tertius tendon ! Extensor digitorum longus tendon ! Extensor hallucis longus tendon ! Tibialis anterior tendon

o Medial ! Tibialis posterior tendon ! Flexor digitorum longus tendon ! Flexor hallucis longus tendon

o Posterior ! Calcaneal tendon

• Joint capsule • Neurovascular supply

o Posterior tibial artery and fibular arteries o Posterior tibial nerve, medial plantar nerve, and sural nerves

• Ligaments

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o Lateral talocalcaneal ligament o Calcaneofibular o Interosseous talocalcaneal ligament o Cervical ligament

• Bones o Talus o Calcaneus

Table 8. Joint Motions at the Subtalar Joint

Biomechanics of the Subtalar Joint

The large, complex articular structure of the subtalar joint has unique impacts on the function of the subtalar joint. The articular surface consists of three sets of facets that articulate between the inferior talus and the superior calcaneus, consisting of posterior facets, middle facets, and anterior facets, one of each on the talus and one of each on the calcaneus. The posterior facets are the largest articulation, covering 70% of total articular surface area, and 50-‐75% of weight bearing is through this joint. The posterior facet of talus is concave, and the posterior facet of calcaneus is largely convex with slight concavity posteriorly (Figure 15). It is held tightly in place by this interlocking concave/convex relationship, as well as ligaments, the forces of body weight, and activated muscles surrounding the ankle joint. The middle facets and anterior facets are significantly small in comparison with the posterior facet. The anterior and middle facets of the calcaneus are very mildly concave on the calcaneus and convex on the talus. The middle facet on the superior surface of calcaneus is just anterior to the sustentaculum tali, a bony outcropping on the calcaneus under which the flexor hallucis longus tendon courses. The tarsal canal is a funnel-‐shaped bony tunnel that runs obliquely in the inferior talus and superior calcaneus. It separates the posterior facets from the anterior and middle facets into two separate joint cavities. It’s

Joint Motion Primary Movers Secondary Movers Inversion of the ankle

Tibialis posterior Tibialis anterior

Eversion of the ankle

Fibularis longus, Fibularis brevis

Fibularis tertius

Figure 15. Joint surfaces of the subtalar joint

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large end is known as the sinus tarsi, which is located just anterior to the lateral malleolus, and the small end is posterior and below the medial malleolus, above sustentaculum tali.

Even though all three articulations all contribute to motion at the subtalar joint, the posterior facet has significantly more motion and as a result is the primary focus clinically in regards to increasing rearfoot mobility via mobilizations.

The ligamentous structures of the subtalar joint are located both intrinsically between the calcaneus and the talus as well as extrinsically surrounding the ankle complex (Figure 16). As a result the subtalar joint is largely supported and rarely dislocates. The intrinsic ligaments of the joint occur within the tarsal sinus and are recognized as primary stabilizers of the joint, further supported by extrinsic ligaments of the ankle region. The interosseous talocalcaneal and cervical ligaments attach directly between the talus and calcaneus, both providing stability by limiting motion in all directions, especially inversion (See ligaments of the subtalar joint). There is also a lateral talocalcaneal ligament, but it is not always present. The interosseous ligament is more medial in the canal. The cervical is the strongest of the intrinsic ligaments of the subtalar joint. It is in the anterior portion of the tarsal sinus, where it joins the neck of the talus to the neck of the calcaneus (hence the name, “cervical”).

External ligaments of the ankle do not attach directly between the talus and calcaneus, but are relevant in that they limit the motions of inversion and eversion that occur mainly at the subtalar joint. The lateral ligaments that prevent inversion are the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament (Figure 17). The strong, broad deltoid ligament limits eversion.

The range of motion (ROM)

at the subtalar joint varies depending on whether it is active or passive. Inversion is usually almost double that for eversion during active ROM, and is 3:1 inversion to eversion in passive ROM. The reasons for the much larger range into inversion is due to the distally projecting lateral malleolus and the strong, broad deltoid ligament medially, which act on both sides of the joint to limit calcaneal eversion. In comparison, the lateral ligaments of the ankle are smaller and cover much less surface area in comparison to the deltoid ligament.

Figure 18. Axis of rotation about the subtalar joint

Figure 16. Ligaments of subtalar joint

Figure 17. Ligaments of lateral ankle

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The arthrokinematics of the subtalar joint involves the sliding motion among three sets

of facets. This creates a curvilinear arc of movement about an oblique axis. The axis of rotation begins from the lateral-‐posterior heel, and travels superiorly,

medially and anteriorly through the subtalar joint (Figure 18). The axis is 42°from horizontal plane and 16° from the sagittal plane. The alternating convex-‐concave facets create a screw-‐like, rotatory motion at the subtalar joint. This allows for the triplanar motions of supination and pronation to occur in an arc about this axis (Figure 19). This joint is interesting in that since the concave surface of the talus moves on the convex posterior facet of the talus, one would expect it to glide in the same direction as it is rolling (this is what one would theoretically expect in a concave moving on convex relationship). However, if this were to happen it would counteract the action one would expect of the mildly convex anterior and middle facets of the talus moving on the mildly concave surface of the calcaneus, which would be to roll and glide in opposite directions (a convex surface moving on a concave surface). This results in a twisting motion that requires the facets to move simultaneously in opposite motions across their articular surfaces.

Therefore, the triplanar motions involved in supination and pronation cannot occur individually but must occur in concordance with one another as the talus (or calcaneus in non-‐weight bearing) twists across the three articular surfaces.

The motions of supination are adduction, plantar flexion and inversion. The motions of pronation are abduction, dorsiflexion and eversion. Adduction/abduction and inversion/ eversion are most prevalent at the subtalar joint, whereas dorsiflexion and plantar flexion at the subtalar joint is very slight and usually ignored clinically. In supination, the subtalar joint surfaces are held tightly together by ligamentous tension in their close packed position. During gait, the foot is supinated as it pushes off to provide a rigid lever with which to transmit maximal force. However, this supination rapidly changes to pronation when the foot hits the ground, allowing for shock absorption. This alternating between supination and pronation is important for proper force delivery and shock absorption during gait.

The pitch of the oblique axis of rotation can explain the motions prevalent at the subtalar joint. Since the axis is 42° from the horizontal plane and 16° from the sagittal, it has both anterior to posterior and superior to inferior directionality, but minimal medial to lateral directionality (Figure 20). This creates motion in a combination of the frontal and transverse planes, with little motion in the sagittal plane. What manifests as a result is a combination of abduction and eversion or adduction and inversion, with

Figure 19. Pronation and supination about the oblique axis of rotation. Posterior view of right foot.

Figure 20. Pitch of oblique axis of rotation of the subtalar joint in the horizontal (left) and sagittal (right) planes

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minimal dorsiflexion and plantar flexion contribution. Since the subtalar joint is weight bearing, let us consider the effects of open kinetic

chain and closed kinetic chain motion and how it affects motion at this joint. Motion in open chain is relatively simple, with the calcaneus moving about the oblique axis in relation to a talus stabilized in the talocrural mortise.

Motion in closed chain is more complex; the calcaneus is immobile due to the load of body weight. Consequently, pronation and supination occur by rotation in the transverse plane of the talus and, since the talocrural joint can only accommodate dorsiflexion and plantar flexion, the rotatory component is transmitted up the tibia. As a result, when supination occurs in weight bearing, the inversion moment of the calcaneus under the talus results in external rotation of the leg (Figure 21). Without the rotation of the subtalar joint, the foot would spin on the ground or there would be damage to the mortise of the talocrural joint. As the foot is pronated in weight bearing, the motion of the talus will cause a medial rotation of the tibia, since the calcaneal eversion moment is coupled with internal rotation of the tibia (Figure 21). One can infer that these resulting rotational forces will have implications at both the knee and hip joints. Table 9. Ligaments of the Subtalar Joint


Calcaneofibular ligament

From lateral malleolus to tubercle of lateral calcaneus

Lateral talocalcaneal ligament

From the lateral process of the talus to the lateral calcaneus

Stabilizes subtalar joint

Resist inversion of the ankle

Interosseous talocalcaneal ligament

From the calcaneal sulcus to the talar sulcus

Limit all excessive motions, mainly inversion

Resists supination and inversion of the ankle

Cervical ligament From the anterior sinus tarsi to the inferior and medial neck of the talus

Limit all excessive motions, mainly inversion

Resists supination of the subtalar joint

Tibiocalcaneal (Deltoid ligament)

From medial malleolus to sustentaculum tali

Stabilizes joint & limits talar abduction

Resist eversion of the ankle

Figure 21. Closed kinetic chain motions of the subtalar joint

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Common Pathology of the Subtalar Joint Clubfoot

Clubfoot is a congenital condition in which the foot is held in an abnormal, twisted position. There are multiple types of clubfoot, and it can occur due to neurological or musculoskeletal causes. In talipes equinovarus (clubfoot), the foot is in an inverted, plantar flexed position, with the forefoot adducted and curved medially (Figure 22). The calcaneus is

small and in the varus position. The incidence is 1-‐2/1000 live births and affects males more often than females, and in half of the cases there are bilateral malformations. There is also calf atrophy and the anterior tibial artery and dorsalis pedis are often absent or small. The affected foot exhibits shortness and tightness of surrounding musculature, tendons and ligaments, and also in the posterior foot and ankle and medial joint capsule. With this pathology, one cannot put the foot flat on the floor. Rather, they must walk on the lateral surface of the foot, which is painful. The most common and effective treatment is currently

the Ponseti method (Figure 23), which involves a series of casts to realign the tissue, followed by bracing.

Tarsal Tunnel Syndrome Tarsal tunnel syndrome is caused by compression and

irritation of the tibial nerve as it passes around the talus (Figure 24). The symptoms mirror that of carpal tunnel syndrome in the wrist and hand with numbness and tingling and often pain. Due

to the vague nature of symptoms, this syndrome is often misdiagnosed as other foot and ankle pathologies. According to Hudes in 2010, it is unclear what causes tarsal tunnel but those who overpronate or have a history of ankle sprains are more likely to develop this syndrome due to stressed on the medial aspect of the ankle. If left untreated, tarsal tunnel can lead to permanent nerve damage and

loss of sensation.

Figure 22. Talipes equinovarus presentation

Figure 24. Tarsal tunnel location

Figure 23. Ponseti method of serial casting

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Introduction to the Foot The ankle and foot complex is comparable to the

wrist and hand complex of the upper extremity. While the foot structure is remarkable in that it can bear the weight of a human being, what truly makes the foot extraordinary is its ability to provide mobility as well as stability. The foot works with the ankle to produce stability in weight-‐bearing by providing a stable base of support and creating a rigid lever for the push-‐off stage in bipedal gait. On the other hand, the foot can reduce or redirect forces imposed by proximal lower extremity joints, absorb weight-‐bearing forces, and adapt its structure to conform to uneven surfaces.

All of these amazing feats are accomplished by a total of 25 joint articulations and over 28 bones (Figure 1). For the purposes of this guide, the ankle complex will consist of the following joints: the proximal and distal tibiofibular joints, the talocrural joint, and the subtalar joint. The foot will consist of the transverse tarsal joint, the distal intertarsal joint, the intercuneiform and cuneocuboid complex, the five tarsometatarsal joints, the five metatarsophalangeal joints, the four intermetatarsal joints, and the nine interphalangeal joints. The foot can be divided into three distinct regions: hindfoot, midfoot, and forefoot. The hindfoot is composed of the talus and calcaneus; the midfoot is composed of the navicular, cuboid, and three cuneiform bones; the forefoot is composed of the metatarsals and the phalanges.

The foot receives blood from the dorsal artery of the foot and its tributaries on the dorsal surface and the posterior tibial artery and its tributaries on the plantar surface. The blood supply to specific joints will be discussed later in this section. Branches of the sciatic nerve innervate the foot. The sciatic nerve arises from the ventral root of spinal segments L4-‐L5. The tibial branch of the sciatic nerve and its branches innervate the plantar surface of the foot: the medial and lateral plantar nerves. The deep fibular branch of the common fibular nerve innervates the dorsal surface of the foot. Specific innervations for each joint will be discussed later in this guide. Muscles Acting on the Foot The musculature acting on the foot is commonly broken into extrinsic muscles and intrinsic muscles. The extrinsic muscles have origins outside of the foot but play a role in joint motion at the foot. These muscles are shown in the muscle table of the ankle joint. The intrinsic muscles of the foot originate and insert in the foot, causing motion solely at the joints of the foot, shown below.

Figure 1. Bones of the foot

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Table 1. Intrinsic Muscles of the Foot

Muscle Proximal Attachment

Distal Attachment

Segmental Innervation

Peripheral Innervation

1st Layer

Abductor Hallucis

Medial tubercle of the calcaneal tuberosity; flexor retinaculum; plantar aponeurosis

Medial aspect of the base of the proximal phalanx of the 1st digit

S2, S3 Medial Plantar Nerve

Flexor Digitorum Brevis

Medial tubercle of the calcaneal tuberosity; plantar aponeurosis; intermuscular septa

Both sides of the middle phalanges of the lateral four digits


Abductor Digiti Minimi

Medial and lateral tubercles of the calcaneal tuberosity; plantar aponeurosis; intermuscular septa

Lateral aspect of the base of the proximal phalanx of the 5th digit

S2, S3 Lateral Plantar Nerve

2nd Layer

Quadratus Plantae

Medial surface and lateral margin of the plantar surface of the calcaneus

Posterolateral margin of the tendon of flexor digitorum longus


S2, S3 Medial one: Medial Plantar Nerve Lumbricals Tendons of flexor

digitorum longus

Medial aspect of the expansion over the lateral four digits S2, S3

Lateral three: Lateral Plantar Nerve

3rd Layer

Flexor Hallucis Brevis

Plantar surfaces of the cuboid and lateral cuneiform

Both sides of the base of the proximal phalanx of the 1st digit


Oblique head; bases of metatarsals 2-‐4

Adductor Hallucis

Transverse head; plantar ligaments of metatarsophalangeal joints

Lateral aspect of the base of the proximal phalanx of 1st digit

S2, S3 Deep branch of Lateral Plantar Nerve

Flexor Digiti Minimi Brevis

Base of 5th metatarsal Base of the proximal phalanx of 5th digit

S2, S3 Superficial branch of Lateral Plantar Nerve

4th Layer

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Plantar Interossei (3)

Bases and medial aspects of the 3rd – 5th metatarsals

Medial aspect of bases of the phalanges of 3rd-‐5th digits


1st: medial aspect of the proximal end of phalanx of 2nd digit Dorsal

Interossei (4) Sides of the 1st – 5th metatarsals

2nd – 4th: lateral aspects of 2nd – 4th digits


Dorsum of the Foot Extensor Digitorum Brevis

Long extensor tendons of the 2nd – 4th medial digits

Extensor Hallucis Brevis

Calcaneus; interosseous talocalcaneal ligament; inferior extensor retinaculum

Dorsal aspect of the base of the proximal phalanx of the 1st digit

L5 or S1, or L5 and S1

Deep Fibular Nerve

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The Transverse Tarsal Joints: Talonavicular and Calcaneocuboid The transverse tarsal joint (Figure 2), also referred to as the

midtarsal joint, involves two separate articulations. The talonavicular joint makes up the medial articulation, while the calcaneocuboid joint makes up the lateral articulation. Together these joints form an S-‐shaped joint line that demarcates the midfoot and forefoot from the hindfoot. The image to the right depicts this relationship. Both the talonavicular joint and the calcaneocuboid joint are synovial joints and the biomechanics of these articulations allow for the transverse tarsal joint to move in the transverse plane to produce inversion and eversion of the midfoot. Talonavicular Joint The talonavicular joint can be considered a ball and socket joint based on some of its structural relationships. The convex head of the talus creates the proximal aspect of the talonavicular joint, while the concave, posterior aspect of the navicular makes up the distal portion. These joint surfaces, as well as the articulation of the inferior talus with the anterior and medial facets of the calcaneus, are surrounded by one joint capsule. The capsule itself is maintained or reinforced by a series of ligaments. The dorsal talonavicular ligament provides support dorsally. The interosseous ligament provides support posteriorly. The bifurcated ligament supports the joint laterally. Finally, the deltoid ligament reinforces the capsule medially. Calcaneocuboid Joint The calcaneocuboid joint has less of an ability to move than the talonavicular joint because of its joint surfaces. The articulation is created by the anterior surface of the calcaneus proximally and the posterior surface of the cuboid distally. Every articular surface of the calcaneocuboid has a concave and convex configuration and thus forms, as Neumann put it, an interlocking wedge that resists sliding and provides stability to the lateral column of the foot. The calcaneocuboid is also a synovial joint surrounded by a capsule. A separate set of ligaments reinforces this joint. The bifurcated ligament supports the capsule distally. The long and short plantar ligaments support the plantar side of the capsule. Finally, the dorsal calcaneocuboid ligament reinforces the capsule dorsal-‐laterally. The transverse tarsal joint receives its blood supply from the medial and lateral plantar arteries that originate from the posterior tibial artery (Figure 3). These joints are innervated by the medial and lateral plantar

Figure 2. Transverse tarsal joint

Figure 3. Blood supply

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nerves, which are branches of the tibial nerve, originating from the sciatic nerve. They also receive innervation from the deep fibular nerve on the dorsal aspect. Tissue Layers from Superficial to Deep


• Superficial Fascia o Subcutaneous Tissue

! Adipose ! Neurovasculature ! Loose Connective Tissue

• Dorsal Fascia o Inferior Extensor Retinaculum

• Dorsal Muscles o Dorsum of the Foot

! Tendon of Tibialis Anterior ! Tendon of Extensor Hallucis Longus ! Extensor Hallucis Brevis Muscle ! Tendons of Extensor Digitorum Longus ! Extensor Digitorum Brevis Muscle ! Tendon of Fibularis Tertius ! Tendon of Fibularis Brevis

• Neurovasculature o Deep Fibular Nerve o Dorsalis Pedis

• Ligaments o Deltoid Ligament o Dorsal Talonavicular Ligament o Bifurcate Ligament

• Joint Capsule o Synovial membrane o Synovial fluid o Articular cartilage

• Bones o Talus o Navicular o Cuboid


• Ligaments o Long and Short Plantar Ligaments o Plantar Calcaneocuboid Ligament

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o Plant Cuboideonavicular Ligament • Neurovasculature

o Medial Plantar Nerve o Lateral Plantar Nerve o Medial Plantar Artery o Lateral Plantar Artery

• Plantar Muscles o First Layer

! Abductor Hallucis Muscle ! Flexor Digitorum Brevis Muscle ! Abductor Digiti Minimi Muscle

o Second Layer ! Quadratus Plantae Muscle

o Third Layer o Fourth Layer

• Plantar Fascia • Superficial Fascia

o Subcutaneous Tissue ! Adipose ! Neurovasculature ! Loose Connective Tissue

• Hypodermis • Dermis • Epidermis

Table 2. Joint Motions at Talonavicular and Calcaneocuboid Joints


Inversion Tibialis Posterior Tibialis Anterior

Extensor Hallucis Longus Flexor Digitorum Longus Flexor Hallucis Longus

Eversion Fibularis Longus Fibularis Brevis

Extensor Digitorum Longus Fibularis Tertius

Biomechanics and Kinematics of the Talonavicular Joint The two transverse tarsal joints (the lateral will be described in more detail later) move in synergy. In an open kinetic chain position, these joints, together with the subtalar joint, move to create the combined motions called supination and pronation. Both of these motions can occur in a closed kinetic chain position as well where the subtalar joint is fixed. These unique movements are made up of three other, smaller, contributing movements that happen together to create the aforementioned combined motions. One other important piece of information is that the ability of this joint to stabilize the mid-‐foot depends upon the relative position of the subtalar joint. Thus, dysfunction of the subtalar joint affects the biomechanical efficiency of the transverse tarsal joints.

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For supination (Figure 4), adduction and plantar flexion occur at these joints about the oblique axis (described below) while inversion occurs about the longitudinal axis (also described below). In the other direction, pronation (Figure 5) is made up of dorsiflexion and abduction about the oblique axis, and eversion about the longitudinal axis. Each of these motions may, to some small degree, occur by themselves at the transverse tarsal joints, but are more likely to occur together. In open kinetic chain scenarios, the arthrokinematic motions occurring at this joint will happen in the same direction since the concave navicular will be moving on the convex talus. When closed chain situations arise, the same arthrokinematic motions will move in the opposite direction, with the convex talus moving on the fixed, concave navicular. The ability for this joint to move about these axes and in three different directions is a crucial part of gait. It gives

the foot the ability to adapt to uneven terrain, providing the most biomechanically advantageous position for the foot to distribute the forces transmitted through it, and prepare for stability through the stance phases of gait ending with push-‐off (rapid ankle plantar flexion). Since the motions of plantar flexion and dorsiflexion, eversion and inversion, and abduction and adduction are so difficult to isolate at this joint, it is hard to measure the exact degree or normative values for range of motion. However, there should be about twice as much supination range of motion available than pronation range of motion. This is similar to the motion available at the subtalar joint where 20-‐25 degrees of inversion, and 10-‐15 degrees of eversion, are available. Pronation will be primarily accomplished with the contraction of the fibularis longus muscle due to its cross-‐sectional area and line of pull. The fibularis brevis and tertius muscles will each

contribute to this combined motion, but play smaller roles. Supination, on the other hand, calls upon the tibialis posterior with its optimal cross-‐sectional area and line of pull. It is aided by the tibialis anterior, flexor digitorum longus, and triceps surae to smaller degrees. Joint Configuration and Planes of Motion The convex talar head, plantar calcaneonavicular ligament, and concave proximal navicular articulate to form a ball-‐and-‐socket joint. The support of the plantar calcaneonavicular ligament, also commonly known as the spring ligament, is crucial for the integrity of this joint by maintaining the position of the talar head in weight bearing. It lies along the plantar and medial aspects of the joint.

Figure 6. Transverse tarsal axes of motion

Figure 4. Supination

Figure 5. Pronation

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There is also a joint capsule of uneven shape surrounding the talonavicular joint. This capsule receives reinforcement posteriorly, dorsally, laterally, and medially from the subtalar interosseous ligament, dorsal talonavicular ligament, the calcaneonavicular fibers of the bifurcated ligament, and the anterior (or tibionavicular) fibers of the deltoid ligament respectively. There are two planes of motion that are unique to the medial and lateral transverse tarsal joints. Eversion and inversion occur about the longitudinal axis (Figure 6). About the oblique axis, combined movements of abduction and dorsiflexion, and adduction and plantar flexion happen when movement occurs in the opposite direction. Table 3. Ligaments of the Talonavicular Joint (Figure 7)


Plantar calcaneonavicular or “Spring”

Talar shelf to the inferior margin of the posterior articular surface of the navicular

Supports the head of the talus, transfers weight from the talus, and helps maintain the longitudinal arch of the foot

Dorsal Talonavicular

From the anterior surface of the talus to the superior and anterolateral surface of the navicular

Helps maintain the navicular in its position superiorly and helps keep the joint approximated

Tibionavicular part of the Deltoid

From the inferior surface of the medial malleolus to the posteromedial surface of the navicular

Helps maintain the navicular in its position superomedially and helps keep the joint approximated

Bifurcated Anterolateral surface of the talus to the dorsolateral surface of the navicular

Helps maintain the navicular in its position superomedially and helps keep the joint approximated

Common Joint Pathologies of the Talonavicular Joint Stress fractures

These can occur at any of the bones in the foot, but will be listed here only, to avoid repetition. Stress fractures happen in a variety of populations for reasons such as poor biomechanics, over-‐pronation, poor or old shoes, overuse or over-‐training, an increase or change in training level, inadequate rest between stressful events, and high impact exercise like repetitive

Figure 7. Medial view of talonavicular ligaments

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running or jumping. Symptoms generally present as pain with standing or activity, swelling, and tenderness to palpation. Symptoms should decrease with rest and cessation of the aggravating activity.

Typical treatment for this condition is cessation of the aggravating activity. Non-‐weight bearing activities, such as swimming, can be done since force isn’t distributed through the injured bone so long as they are pain-‐free. Most patients are given a walking boot for 6-‐8 weeks or more and, if that doesn’t work, may be placed in a cast. Surgery to fix the bone with a screw is a last resort. Pes Planus A.K.A. Flat Feet

This condition occurs due to a laxity of the ligamentous structures that normally provide structure and form to the mid-‐tarsal joints. The laxity, along with gravity, leads to a position of relative pronation (Figure 8). Symptoms in adults can present as tiredness or soreness in the feet after prolonged periods of activity or standing. This position is not biomechanically advantageous, as it doesn’t provide the appropriate structure or transmission of forces needed during gait and other impact activities.

Treatment for this condition includes triceps surae stretching, modalities, balance and neuromuscular re-‐training activities, strengthening of the ankle stabilizing muscles and the hip abductors, and functional retraining. Orthotics can also provide a great deal of relief and allow patients to participate with little to no symptoms. Pes Cavus

Pes cavus (Figure 9) is, as described in a study by Piazza et. al. in 2010, “characterized by a high arch of the foot that does not flatten with weight bearing” that “can be located in the forefoot, midfoot, hindfoot, or in a combination of all these sites… with [a] prevalence [in the general population] of approximately 10%”. It is a common condition that suggests a neurological disorder, like Charcot-‐Marie-‐Tooth disease, may exist. Symptoms include pain, frequent ankle sprains, calluses, hammertoes or claw toes, and foot drop.

Non-‐surgical treatment includes bracing, orthotics, manual therapy, strengthening of surrounding weak musculature, modalities, and shoe modifications. As a last resort, surgery may be considered to increase range of motion, decrease pain, and increase functionality.

Figure 8. Pes planus

Figure 9. Pes cavus

Figure 15. Pes Cavus

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Calcaneocuboid (Lateral Transverse Tarsal) Joint (Figure 10) Biomechanics and Kinematics of the Calcaneocuboid Joint The biomechanics/ kinematics of the lateral transverse tarsal, or calcaneocuboid, joint are the same as described in the section about the biomechanics of the medial transverse tarsal joint. Briefly, the motion about this joint works harmoniously with both the talonavicular and subtalar joints. Supination (made up of plantar flexion, inversion, and adduction) and pronation (made up of abduction, dorsiflexion, and eversion) are the

motions produced at this joint. Mobility at this joint is crucial to the ability of the foot to adapt to uneven terrain, appropriately distribute forces through the foot throughout stance phases of gait, and provide stability. The biomechanics related to muscles that create supination and pronation movements were described previously in the biomechanics/kinematics section with the talonavicular joint and should be regarded as the same.

Joint Configuration and Planes of Motion Like the talonavicular joint, the calcaneocuboid joint works around two, unique axes of rotation: the oblique and longitudinal. Eversion or inversion occurs about the longitudinal axis. Both abduction or adduction, and plantar flexion or dorsiflexion, occur about the oblique axis. These motions rarely occur independent of each other, but summate to form the motions called supination and pronation. Pronation consists of the dorsiflexion, abduction, and eversion components, and supination the motions of plantar flexion, inversion, and adduction. In contrast to the talonavicular joint, the calcaneocuboid joint allows less motion to occur in the frontal and horizontal planes. This occurs because of the nature of the articulation between the anterior surface of the calcaneus and the proximal portion of the cuboid. The calcaneus and cuboid each have a convex and concave curvature that creates an interlocking wedge resistant to sliding motions. The stability and relative inflexibility created by this juncture assists the lateral column of the foot. Some sources list this joint as a synovial, saddle joint, while others mention that it is a planar, synovial joint. These differences may be due to differences in bony structure from person to person. The lateral transverse tarsal joint receives support from a joint capsule. The capsule is further strengthened by its connection dorsally and laterally to the dorsal calcaneocuboid ligament. Additional stabilization comes from the bifurcated ligament, the long plantar ligament, and the short plantar, or plantar calcaneocuboid, ligament. These ligaments are described in more detail in the table below.

Figure 10. Transverse tarsal joints

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Table 4. Ligaments of the Calcaneocuboid Joint (Figure 11) Ligament Attachments Function

Dorsal calcaneocuboid

From the anterolateral surface of the calcaneus to the superior surface of the cuboid

Reinforcement of the joint capsule dorsally and laterally

Bifurcated Anterolateral surface of the talus to the posterior dorso-‐medial surface of the cuboid

Reinforcement of the calcaneocuboid joint dorsally

Long plantar Plantar surfaces of the calcaneus and cuboid to the metatarsal bases

Reinforcement of the plantar surface of the joint and helps maintain the longitudinal arch of the foot

Short plantar or Calcaneocuboid

Anterior aspect of the plantar surface of the calcaneus to the plantar surface of the cuboid

Reinforcement of the plantar surface of the joint and helps maintain the longitudinal arch of the foot

Common Joint Pathologies of the Calcaneocuboid Joint Talipes Equinovarus

Talipes equinovarus is a condition that presents at birth and is more common in males than females. A more common term for this condition is clubfoot deformity. Patients will present with an adducted and supinated midfoot, ankle plantar flexion, and calcaneal internal rotation and inversion. In a study by Simons (1995), the deformity was described as “a combination of medial angulation of the calcaneocuboid joint with medial subluxation of the cuboid on the calcaneus”.

Outcomes for recovery from this condition are very good when treatment begins within the first two weeks of birth, and not later than 9 months of life. Standard treatment in the U.S. follows the Ponsetti method, which involves casting, taping, splinting, and surgery when conservative management fails. Casting is followed by weekly manipulation and another cast. Further bracing after the serial casting occurs for 3-‐4 months full-‐time, and at night for 2-‐4 years.

Figure 11. Lateral view of calcaneocuboid ligaments

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The Distal Intertarsal Joints: Cuneonavicular, Cuboideonavicular, Intercuneiform, and Cuneocuboid Joints The distal intertarsal joint (Figure 12) is distal in relation to the previously mentioned transverse tarsal joint. Three unique joint complexes make up the articulations associated with the distal intertarsal joints. These articulations include the cuneonavicular joint, the cuboideonavicular joint, and the intercuneiform and cuneocuboid joint complex. It has been stated that the functions of this group of joints includes assisting the transverse tarsal joint in creating the combined motions of pronation and supination of the midfoot. By creating the boney structure of the transverse arch of the foot, the distal intertarsal joint also provides significant structure to the midfoot during weight bearing. Cuneonavicular Joint The most medial element of the distal intertarsal joint, the joining of the distal, anterior surface of the navicular bone with the proximal, posterior surfaces of the three cuneiform bones creates the cuneonavicular joint. Each of the cuneiforms (medial, intermediate, and lateral) has slightly concave facets that articulate with three slightly convex facets on the navicular bone. The stability of this joint is created by these “locking” articulations, but is also reinforced by plantar and dorsal ligaments. Overall, the cuneonavicular joint helps to connect and transmit the movement of the midfoot to the forefoot. Cuboideonavicular Joint The most lateral component of the distal intertarsal joint is the cuboideonavicular joint. This synovial joint can be described as the articulation between the lateral aspect of the navicular bone and the medial aspect of the cuboid bone. The joint surfaces move against each other during inversion and eversion of the midfoot. Intercuneiform and Cuneocuboid Joint Complex The intercuneiform and cuneocuboid joint complex form the middle portion of the distal intertarsal joint. A total of three articulations make up this complex. There are two articulations between the three cuneiform bones and one articulation created between the lateral cuneiform and the medial surface of the cuboid bone. The interacting joint surfaces in all three articulations can be seen as essentially flat. Neumann notes that they are fundamentally aligned in parallel with the long axis of the metatarsals. As depicted on the previous page, the intercuneiform and cuneocuboid complex creates the transverse arch of the foot. During weight bearing, the transverse arch (Figure 13) can depress or bow to help distribute the weight of the body over the five metatarsal bones

Figure 12. Distal intertarsal joints

Figure 13. Transverse arch

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distally. The intermediate cuneiform acts as a wedge-‐shaped keystone to hold the entire structure together. Beyond its boney structure, connective tissue and the intrinsic and extrinsic muscles of the foot support the arch. The distal intertarsal joints receive blood supply from the medial and lateral tarsal arteries that originate from the anterior tibial artery. The plantar surface receives blood from the medial and lateral plantar arteries. These joints are innervated by the lateral branch of the deep fibular nerve, which originates from the common fibular nerve off of the sciatic nerve on the dorsal surface. The joint also receives innervation from the medial and lateral plantar nerves on the plantar surface. Tissue Layers Superficial to Deep

• Epidermis • Dermis • Hypodermis • Superficial Fascia




! Tendon of Tibialis Anterior ! Tendon of Extensor Hallucis Longus ! Extensor Hallucis Brevis Muscle ! Tendons of Extensor Digitorum Longus ! Extensor Digitorum Brevis Muscle ! Tendon of Fibularis Tertius

• Neurovasculature o Lateral branch of Deep Fibular Nerve o Dorsalis Pedis o Medial Tarsal Artery o Lateral Tarsal Artery

• Ligaments o Dorsal Cuboideonavicular o Dorsal Cuneonavicular Ligaments o Dorsal Intercuneiform Ligaments


• Bones o Medial Cuneiform o Intermediate Cuneiform o Lateral Cuneiform

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o Navicular o Cuboid


• Ligaments o Long and Short Plantar Ligaments o Plantar Cuneonavicular Ligament o Plantar Cuboideonavicular Ligament

• Neurovasculature o Medial Plantar Nerve o Lateral Plantar Nerve o Medial Plantar Artery o Lateral Plantar Artery



o Second Layer ! Quadratus Plantae Muscle

o Third Layer o Fourth Layer

• Plantar Aponeurosis • Superficial Fascia



Table 5. Joint Motions at the Cuneonavicular and Cuboideonavicular Joints

Joint Motion Primary Movers Secondary Movers Pronation Fibularis Longus Fibularis Brevis, Fibularis Tertius Supination Tibialis Posterior Tibialis Anterior Table 6. Joint Motions at the Intercuneiform and Cuneocuboid Joint Complex

Joint Motion Primary Movers Secondary Movers Glide (Muscles provide stability to the complex)

Tibialis Posterior Fibularis Longus, Fibularis Brevis, Fibularis Tertius

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Cuneonavicular Joint

Biomechanics and Kinematics of the Cuneonavicular Joint (Figure 14) Motion occurring at this joint assists in transferring pronation and supination movements from the transverse tarsal joint to the forefoot. Another function of this joint is to provide stability for the foot during activity. The muscles responsible for these motions and their biomechanics have been described previously, but, in brief, are primarily the tibialis posterior for supination and fibularis longus for pronation. The associated secondary movers were also described previously.

Joint Configuration and Planes of Motion Very little motion occurs at the

cuneonavicular joint. The articulation of the slightly convex navicular facets proximally and the distal, concave cuneiforms allow for minimal, gliding motions in this planar, synovial joint. Inconsequential for movement, but not for stability, motion may occur superiorly and inferiorly, and medially and laterally. Although most motion at these joints can be insignificant, one study by Phillips et. al. found that “plantar flexion motion between the first [medial] cuneiform and the navicular is significant and comprises most of the plantar flexion motion of the first ray during propulsion”. Reinforcement of the joint comes via plantar and dorsal ligaments and a general, fibrous, joint capsule. Table 7. Ligaments of the Cuneonavicular Joint

Ligament Attachment Function

Plantar Cuneonavicular/Tarsal

From the plantar surface of the navicular to the cuneiforms and from one cuneiform to another

Restrict motion inferiorly and provide support to the cuneonavicular joint

Dorsal Cuneonavicular/Tarsal

From the dorsal surface of the navicular to the cuneiforms and from one cuneiform to another

Restrict motion superiorly and provide support to the cuneonavicular joint

Common Joint Pathologies of the Cuneonavicular Joint No significant pathologies commonly occur at this joint. Other conditions mentioned throughout this work, that may also occur here, have been described in detail elsewhere.

Figure 14. Cuneonavicular Joint

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Cuboideonavicular Joint Biomechanics and Kinematics of the Cuboideonavicular Joint

Given that this joint can be either synarthrodial or synovial tells us that there is little motion at this joint. Thus, there are no significant arthrokinematic motions that occur at this joint. Gliding motions of this joint are most noticeable during inversion and eversion movements of the mid-‐foot. Joint Configuration and Planes of Motion The convex cuboid laterally and concave navicular medially form a synarthrodial or synovial (varies from person to person) joint with slight, gliding motions that occur during eversion and inversion of the foot. Significant motion happens only in the coronal plane. Table 8. Ligaments of the Cuboideonavicular Joint


Plantar cubonavicular Plantar surfaces of the medial portion of the cuboid and lateral portion of the navicular

Resist distraction forces

Common Joint Pathologies of the Cuboideonavicular Joint No significant pathologies commonly occur at this joint. Other conditions mentioned throughout this work, that may also occur here, have been described in detail elsewhere. Intercuneiform and Cuneocuboid Complex Biomechanics/Kinematics These articulations form the transverse arch, which stabilizes the mid-‐foot in a transverse plane. Along with the ligamentous support described below, the transverse arch also receives support from the shape of the bones cuneiform and cuboid bones, intrinsic foot muscles, and the tibialis posterior and fibularis longus muscles. Under a load, the transverse arch will depress. This gives the foot the ability to distribute body weight along the five metatarsal heads. The cuneiform region plays a role in important phases of gait at the 1st tarsometatarsal joint, lending to both dispersion of forces and movement during walking. The tibialis posterior muscle will provide stability, with help from the fibularis muscles, during gliding motions of this joint.

Joint Configuration and Planes of Motion The intercuneiform and cuneocuboid complex consists of the articulation between the cuneiforms (lateral and intermediate, and intermediate and medial) Figure 15. Transverse Arch

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and between the lateral cuneiform and cuboid forming a planar, synovial joint. Thus, only gliding motions occur at this joint. No significant convexity or concavity exists between any of these joints, which are supported by plantar, dorsal, and interosseous ligaments. As was mentioned above, this complex forms the transverse arch of the foot (Figure 15), with the intermediate cuneiform being the keystone. Table 9. Ligaments of the Intercuneiform and Cuneocuboid Complex

Ligament Attachment Function

Dorsal tarsals Between each cuneiform and between the cuboid and lateral cuneiform.

Resist distraction forces at each joint.

Plantar tarsals Between each cuneiform and between the cuboid and lateral cuneiform.

Resist distraction forces at each joint.

Interosseous Between each cuneiform. Resist distraction forces between the cuneiforms.

Common Joint Pathologies of the Intercuneiform and Cuneocuboid Complex Transverse arch sprain

An activity or weight-‐related injury distressing the transverse arch that is treated with rest, ice, activity modification, weight loss, arch support, or taping.

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The Tarsometatarsal Joints The tarsometatarsal joints (Figure 16) are collectively referred to as the Lisfranc’s joints. Named after a French surgeon named Jacques Lisfranc, the joints are created by the articulations between the bases of the five metatarsals and the distal articular surfaces of all three cuneiforms, as well as the cuboid bone. The most medial joint is an articulation between the distal aspect of the medial cuneiform and the base of the first metatarsal. The distal aspect of the intermediate cuneiform articulates with the base of the second metatarsal. The distal aspect of the lateral cuneiform articulates with the base of the third metatarsal bone. The distal surface of the cuboid bone actually articulates with both the fourth and fifth metatarsal bases. All five of these joints have flat articulating surfaces in general. The dorsal, plantar, and interosseous ligaments add support. The first tarsometatarsal joint also receives support from its own synovial joint capsule. In general, the Lisfranc’s joints produce dorsiflexion and plantar flexion. The second and third tarsometatarsal joints are the least mobile of the group and this actually provides longitudinal stability during weight bearing. The tarsometatarsal joints receive their blood supply from the medial and lateral tarsal arteries originating from the anterior tibial artery. They may also receive blood from the arcuate artery on the dorsum of the foot. The plantar surface of these joints receives blood from the medial and lateral plantar arteries, originating from the posterior tibial artery. The Lisfranc joints are innervated by the medial and lateral branches of the deep fibular nerve on the dorsum of the foot. They receive innervation from medial and lateral plantar nerves on the sole of the foot. Tissue Layers Superficial to Deep



• Dorsal Fascia • Dorsal Muscles

o Dorsum of the Foot ! Tendon of Tibialis Anterior

Figure 16. Tarsometatarsal joints

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! Tendon of Extensor Hallucis Longus ! Extensor Hallucis Brevis Muscle ! Tendons of Extensor Digitorum Longus ! Extensor Digitorum Brevis Muscle ! Tendon of Fibularis Tertius

• Neurovasculature o Arcuate Artery o Posterior Perforating Branches o Medial Branches of Deep Fibular Nerve

• Ligaments o Dorsal Tarsometatarsal Ligaments


• Bones o Medial Cuneiform o Intermediate Cuneiform o Lateral Cuneiform o Five Metatarsals o Cuboid


• Ligaments o Long Plantar Ligament o Plantar Metatarsal Ligaments

• Neurovasculature o Superficial and Deep branches of the Lateral Plantar Nerve o Superficial and Deep branches of the Lateral Plantar Artery o Superficial and Deep branches of the Medial Plantar Nerve o Superficial and Deep branches of the Medial Plantar Artery



o Second Layer ! Quadratus Plantae Muscle ! Lumbricals

o Third Layer ! Flexor Hallucis Longus Tendon ! Flexor Digitorum Longus Tendon ! Fibularis Longus Tendon

o Fourth Layer

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Table 10. Joint Motions of the Tarsometatarsal Joints


Dorsiflexion Extensor Digitorum Longus Extensor Digitorum Brevis

Plantar Flexion Flexor Digitorum Longus Flexor Digitorum Brevis, Quadratus Plantae

Abduction Tibialis Anterior Fibularis Longus Inversion (1st Metatarsal) Occurs passively with dorsiflexion Eversion (1st Metatarsal) Occurs passively with plantar flexion Biomechanics and Kinematics of the Tarsometatarsal Joints These joints tell very different stories across each of them as far as mobility and support go. The greatest mobility is found in the 1st tarsometatarsal joint, with relatively good mobility also in the 4th and 5th tarsometatarsal joints. The 1st metatarsal has 10 degrees of sagittal plane movement, with little other motion in other directions. This 10 degrees expresses itself as 5 degrees of motion into dorsiflexion during the loading response and mid-‐stance phases of gait. Dorsiflexion at this joint happens when forces due to body weight depress the relatively immobile cuneiforms. This movement also acts as a force re-‐distributor across the medial longitudinal arch, allowing the body to disperse body weight forces. During terminal stance, the opposite motion occurs. Rapid plantar flexion of about 5 degrees (so a 10 degree shift counting the starting point at 5 degrees dorsiflexion) of the 1st tarsometatarsal joint occurs due to the effects of the fibularis longus muscle. This action also provides stability to the medial longitudinal arch by “shortening” it. The stability provided is necessary due to the high loads being borne by the midfoot and forefoot during these phases in the gait cycle. An important note to add is that the plantar flexion and dorsiflexion motions don’t occur in isolation. In both open and closed kinetic chain situations, the 1st tarsometatarsal joint will demonstrate eversion with plantar flexion and inversion with dorsiflexion. These motions are unique and different from supination and pronation at the subtalar and transverse tarsal joints. The inclusion of these motions are heretofore unclear as to their functionality, but the plantar flexion and eversion component may help the foot adjust to irregular walking surfaces. Plantar flexion accomplished via the efforts of the flexor digitorum longus muscle, due to its cross-‐sectional area and line of pull, with help from the flexor digitorum brevis and quadratus plantae muscles. Eversion, which accompanies plantar flexion at this joint, happens passively as plantar flexion occurs. Inversion happens in the same way with dorsiflexion,

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but the prime mover for dorsiflexion is the extensor digitorum longus muscle, with help from the extensor digitorum brevis and extensor hallucis longus muscles.

As was mentioned previously, the 2nd and 3rd tarsometatarsal joints are relatively immobile (Figure 17). This position proves to be advantageous in increasing stability in a longitudinal fashion across the foot that is useful during the terminal phases of gait before forefoot push-‐off. Thus, it can be said that both stability and mobility at the tarsometatarsal joints play important roles throughout all stance phases of gait. Joint Configuration and Planes of Motion The medial, intermediate, and lateral cuneiforms articulate with the bases of the first three metatarsals respectively forming planar, synovial joints. The 4th and 5th metatarsal bases articulate with the cuboid. Out of the 5, tarsometatarsal joints, only the articulation of the 1st metatarsal base and the medial cuneiform has a well-‐developed capsule. The articulating surfaces of the bones, both proximal and distal, are flat. This being said, only planar, gliding motions occur at these joints. But, as was mentioned in the biomechanics section, movement varies at each individual joint from very little to about 10 degrees of total motion.

Table 11. Ligaments of the Tarsometatarsal Joints Ligament Attachments Function

Dorsal tarsometatarsals

From the dorsal surface of the cuneiforms or cuboid to the base of their corresponding distal metatarsal base

Prevent excessive motion superiorly of the metatarsal bases

Plantar tarsometatarsals

From the plantar surface of the cuneiforms or cuboid to the base of their corresponding distal metatarsal base

Prevent excessive motion inferiorly of the metatarsal bases

Interosseous tarsometatarsals

Between adjacent metatarsal bases with some fibers connecting to the cuneiforms or cuboid

Provides support and stability, resisting separation of the metatarsal bases laterally or medially

Common Joint Pathologies of the Tarsometatarsal Joints Lisfranc Injuries

This condition involves rupture of the ligaments supporting the tarsometatarsal joints (also called the Lisfranc region) leading to dislocation and/or a fracture to one of the bones. This can happen at one location (Figure 18) or at multiple sites (middle and right

Figure 17. Tarsometatarsal Joints

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pictures in figure above). A patient who has sustained a Lisfranc injury may present with pain that is worsened with activity, hypermobility, or crepitus with accessory motion testing, swelling and tenderness to palpation on the dorsum of the foot, and bruising on the top or bottom of the foot. Bruising on the bottom of the foot is highly indicative of a Lisfranc injury and suggests that a fracture or complete ligamentous tear (or both) has occurred.

Conservative treatment of this condition consists of a non-‐weight bearing cast and crutches for 6 weeks if the injury doesn’t include dislocation or fracture. Surgical treatment is indicated if any bony displacement or fracture has occurred. Jones Fracture

Stress fractures to components of the tarsometatarsal joints are common, and treatment varies based on severity. The most serious case is called a Jones fracture. A Jones fracture involves a fracture at the base of the 5th metatarsal (an important attachment site for many muscles) between the diaphysis and metaphysis.

This area has poor blood supply and intervention to treat this condition is surgical in nature (Figure 19).

Figure 18. Lisfranc Injuries

Figure 19. Surgical fixation of Jones fracture

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The Intermetatarsal Joints The intermetatarsal joints (Figure 20) are created by the close relationship of the four lateral metatarsals. Much like some of the previous joints in the foot, the intermetatarsal joints receive reinforcement from the planter, dorsal and interosseous ligaments. However, the first and second metatarsals do not exhibit the same amount of proximity, which allows the first digit to have a greater range of motion. The first metatarsal has a structural relationship with the lateral four through the support of the deep transverse metatarsal ligament. These articulations do not produce any true movement, but they provide flexibility to the joints just proximal, the tarsometatarsal joints. The intermetatarsal joints receive their blood supply from the arcuate artery on the dorsum of the foot. The plantar surface of these joints receives blood from the medial and lateral plantar arteries, originating from the posterior tibial artery. These joints are innervated by the digital nerves. Tissue Layers Superficial to Deep




o Dorsum of the Foot ! Tendon of Tibialis Anterior ! Tendon of Extensor Hallucis Longus ! Extensor Hallucis Brevis Muscle ! Tendons of Extensor Digitorum Longus ! Extensor Digitorum Brevis Muscle ! Tendon of Fibularis Tertius

• Neurovasculature o Arcuate Artery o Posterior Perforating Branches

Figure 20. Intermetatarsal joints

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o Medial Branches of Deep Fibular Nerve • Ligaments

o Dorsal Tarsometatarsal Ligaments • Joint Capsule

o Synovial membrane o Synovial fluid o Articular cartilage

• Bones o Medial Cuneiform o Intermediate Cuneiform o Lateral Cuneiform o Five Metatarsals o Cuboid


• Ligaments o Long Plantar Ligament o Plantar Metatarsal Ligaments





o Third Layer ! Flexor Hallucis Longus Tendon ! Flexor Digitorum Longus Tendon ! Fibularis Longus Tendon

o Fourth Layer • Plantar Aponeurosis • Superficial Fascia


• Hypodermis • Dermis

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• Epidermis Table 12. Joint Motions of the Intermetatarsal Joints


Glide

Flexor Digitorum Longus, Flexor Digitorum Brevis, Quadratus Plantae, Extensor Digitorum Longus, Extensor Digitorum Brevis, Tibialis Anterior, Fibularis Longus

N/A

Biomechanics and Kinematics of the Intermetatarsal Joint Since little motion occurs at these joints, the actions of any muscle that crosses them could have an effect on their motion. Motion at these joints may also come from distribution of forces during activity and static weight bearing, as well as from motions at other joints creating small glides at the intermetatarsal joints. Muscles that may have an affect are the flexor digitorum longus and brevis, quadratus plantae, extensor digitorum longus and brevis, tibialis anterior, and fibularis longus. There is no one muscle that has been identified as the primary muscle responsible for motion at these joints. Joint Configuration and Planes of Motion The intermetatarsal joints are formed by the articulation of the bases of the 2nd through 5th metatarsal bases creating small, planar, synovial joints. They are interconnected via plantar, dorsal, and interosseous ligaments. These ligaments also span the gap between the 1st and 2nd metatarsal bases, but there is no articulation between them. Thus, no joint is present at this location. Only small, gliding motions occur at these joints. Table 13.Ligaments of the Intermetatarsal Joints


Plantar intermetatarsals Along the plantar surface of the base of the metatarsals

Inhibit inferior motion of the intermetatarsal joints

Dorsal intermetatarsals Along the dorsal surface of the base of the metatarsals

Inhibit superior motion of the intermetatarsal joints

Interosseous intermetatarsals

Spanning between each adjacent metatarsal base

Prevent distraction forces from separating the adjacent metatarsal bones from each other

Common Joint Pathologies of the Intermetatarsal Joints No significant pathologies commonly occur at these joints. Other conditions mentioned throughout this work, that may also occur at the intermetatarsal joints, have been described in detail elsewhere.

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The Metatarsophalangeal Joints The metatarsophalangeal joints, five in all, are the interaction of the distal heads of every metatarsal bone and the proximal bases of each proximal phalanx (Figure 21). The head of every metatarsal has a convex structure; in contrast, the bases of each proximal phalanx have a concave structure. The joints of each digit are surrounded by articular cartilage, along with paired collateral ligaments. The figure to the right shows the relationship of the joint capsule with the collateral ligaments. The dorsal digital expansion covers the dorsal aspect of every metatarsophalangeal joint and houses the joint capsule and the extensor tendons. Movement at the metatarsophalangeal joints occurs in two planes of motion, about two axes. The joints are capable of dorsiflexion and plantar flexion in the sagittal plane, on the medial-‐lateral axis. The other movements are abduction and adduction in the transverse plane about the vertical axis. The dorsal aspects of these joints receive blood from the dorsal metatarsal arteries that originate from the arcuate artery. The common plantar digital arteries that are derived from the deep plantar arterial arch nourish the plantar aspects of these joints. The dorsal digital branches of the deep fibular nerve innervate the dorsal aspect of these joints. Additionally, the common plantar digital nerves innervate the plantar side of the metatarsophalangeal joints. Tissue Layers Superficial to Deep





! Tendon of Extensor Hallucis Longus ! Tendon of Extensor Hallucis Brevis Muscle ! Tendons of Extensor Digitorum Longus ! Extensor Digitorum Brevis Muscle ! Tendon of Fibularis Tertius

• Neurovasculature o Dorsal Metatarsal Arteries

Figure 21. Metatarsophalangeal joints

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o Dorsal Digital branches of the Deep Fibular Nerve o Lateral Dorsal Cutaneous Nerve

• Ligaments o Dorsal Tarsometatarsal Ligaments o Collateral Ligaments

• Joint Capsule o Extensor Expansions o Synovial membrane o Synovial fluid o Articular cartilage

• Bones o Five Metatarsals o Five Proximal Phalanges o Sesamoid Bones


• Ligaments o Deep Transverse Metatarsal Ligament o Plantar Ligaments





o Third Layer ! Flexor Hallucis Longus Tendon ! Flexor Digitorum Longus Tendon ! Fibularis Longus Tendon ! Adductor Hallucis (Oblique and Transverse Heads)

o Fourth Layer ! Plantar Interossei ! Dorsal Interossei


o Subcutaneous Tissue ! Adipose

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! Neurovasculature ! Loose Connective Tissue


Table 14. Joint Motions of the Metatarsophalangeal Joints


Flexion Flexor Digitorum Longus, Flexor Hallucis Longus, Flexor Digiti Minimi Brevis

Flexor Digitorum Brevis, Flexor Hallucis Brevis, Interossei, Lumbricals

Extension Extensor Hallucis Longus, Extensor Digitorum Longus

Extensor Hallucis Brevis, Extensor Digitorum Brevis

Abduction Abductor Hallucis, Abductor Digiti Minimi, Dorsal Interossei

N/A

Adduction Adductor Hallucis, Plantar Interossei N/A

Biomechanics and Kinematics of the Metatarsophalangeal Joints Each joint can move with two degrees of freedom into either extension or flexion, and abduction or adduction. The movement of these digits is described in relation to the 2nd ray. So, if the 3rd metatarsophalangeal joint moves toward midline, it has adducted. However, if the 1st metatarsophalangeal joint moves in the same direction, the resultant motion is abduction. Passive range of motion in the sagittal plane for these joints can reach 65 degrees of extension and 30-‐40 degrees of flexion. The 1st metatarsophalangeal joint, however, can attain 85 degrees of extension, which may contribute to its susceptibility to the condition described below as “turf toe”. This increase in motion is due, in part to the fact that there isn’t a true articulation between the first and second metatarsals as was described previously. Not having this restriction, like is present in the other four metatarsals, allows for greater flexibility and motion. Extension range of motion at the metatarsophalangeal joints is critical, however, for the “windlass effect” to take place. The windlass effect is described as the mechanism by which the arch of the foot raises off the ground during the terminal phases of gait. Increased tension, which can reach up to 100% of body weight, along the arch increases the stability necessary for push off during rapid

ankle plantar flexion. Without this necessary, tensile stress, even very strong muscles would not be able to lift the heel in the same manner and produce a desirable effect during gait.

Flexion for the 1st metatarsophalangeal joint (Figure 22) is accomplished with the flexor hallucis longus muscle due to its cross-‐sectional area, with help from the flexor hallucis

Figure 22. Metatarsophalangeal Joint

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brevis muscle, even though it has a more direct line of action. Flexion for the rest of the metatarsophalangeal joints requires use of the flexor digitorum longus muscle because of its cross-‐sectional area, with help from the flexor digitorum brevis muscle, even though this muscle also has a better line of pull, as well as the lumbrical and interossei muscles. Abduction for all of the joints calls upon the dorsal interossei muscles, with the abductor hallucis muscle aiding great toe abduction, and the abductor digiti minimi aiding with 5th metatarsophalangeal joint abduction. Extension for joints 2-‐5 uses the extensor digitorum longus muscle, because of its cross-‐sectional area, with help from the extensor digitorum brevis muscle. Extension of the 1st metatarsophalangeal joint calls upon the extensor hallucis longus as its primary mover due to its cross-‐sectional area, with aid from the extensor hallucis brevis muscle. Both of these extensor brevis muscles (digitorum and hallucis) have better lines of pull than their larger counterparts, but have smaller cross-‐sectional area, so they are minor players. Joint Configuration and Planes of Motion Each metatarsophalangeal joint is surrounded by a fibrous capsule that receives reinforcement from collateral ligaments and plantar plates. These joints are synovial, condyloid joints. The collateral ligaments mesh with the capsule. Dorsally, the joints are covered by the dorsal digital expansions, which also blend with the capsule. The articulating surfaces themselves are covered articular cartilage. Five, convex, metatarsal heads articulate with five, concave, proximal phalanges. This means that, in open chain scenarios, the roll and the glide of the proximal phalanx on its corresponding metatarsal head happen in the same direction. In contrast, closed chain arthrokinematics (something you may see in ballerinas or gymnasts) follows the rule that the convex metatarsal head roll and glide happen in opposite direction (roll towards the plantar surface and glide towards the dorsum of the foot). Motion at these joints can occur in the sagittal plane about the mediolateral axis, or about the vertical axis in the horizontal plane. Table 15. Ligaments of the Metatarsophalangeal Joints Ligament Attachments Function

Collaterals

Cord: From the proximal metatarsal head both laterally and medially to the proximal portion of the medial and lateral proximal phalanges (1-‐5). Accessory: From the proximal metatarsal head both laterally and medially to the plantar plate of the proximal phalanges (1-‐5) and sesamoids (in the 1st metatarsophalangeal joint)

Provide restraint to medial and lateral movements at the metatarsophalangeal joint and maintain joint congruity

Deep transverse metatarsals

Horizontal connection between all of the plantar plates and, at the 1st metatarsophalangeal joint, sesamoid bones

Maintains all five of the metatarsophalangeal joints in the same plane of motion for functional use during weight bearing and gait

Superficial To the distal, plantar aponeurosis running Maintains all five of the

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transverse metatarsals

horizontally across the width of the foot at the metatarsophalangeal joints

metatarsophalangeal joints in the same plane of motion for functional use during weight bearing and gait

Dorsal digital expansion

At the metatarsophalangeal joints to the distal phalanx of each toe

Prevents hyperflexion of the MTP, PIP, IP, and DIP joints

Common Joint Pathologies of the Metatarsophalangeal Joints Morton’s Neuroma

This condition may present as tingling or numbness in the tarsal phalanges (commonly between the 3rd and 4th), cramp-‐like pains in the distal foot during prolonged

walking or running, and/or a callus over the affected area that is more prominent than at the same site along other metatarsophalangeal joints (Figure 23). The physical examination will be remarkable for a positive sensation test (lack or diminished sensation distal to the neuroma), a positive compression test reproducing an audible click, decreased sensation, or both, pain relief with removal of shoes or the pressure, and, possibly, tight triceps surae.

Surgical treatment would involve excision of the neuroma, which can lead to re-‐growth (30%) and permanent loss of sensation distal to the excision. Non-‐surgical

treatment includes orthotics, cutouts, triceps surae stretching, cortisone injections, and education on footwear. 1st Metatarsophalangeal Joint Sprain or Turf Toe

This injury is common in athletes and can be caused by repetitive hyperextension of the joint, poor footwear, or forceful hyperextension of the joint (like during a tackle). The patient will have pain with palpation of the joint and, possibly, the flexor hallucis longus or brevis tendons, inappropriate footwear, and tight triceps surae. Pain may also be reproduced with passive extension of the 1st metatarsophalangeal joint or with active flexion of the same. Hallux rigidus

Any trauma to the hallux can lead to hallux rigidus. But, the common mechanism of injury is forceful hyperextension, like in “turf toe”, that can include gradual restriction of motion, degeneration of the articular surfaces, pain, tears of varying degrees to ligaments and tendons, as well as fractures to surrounding bones.

Treatment includes management of pain with modalities, rest, activity modification, footwear change and/or education, strengthening and neuromuscular re-‐education of muscular imbalances and impairments, and stretching of tight musculature.

Figure 23. Morton’s neuroma

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Hallux Abductovalgus or Bunions

Hallux abductovalgus presents as excessive abduction at the 1st metatarsophalangeal joint (Figure 24). The valgus angle is further increased by a deviation of the 1st metatarsal bone towards midline at its distal component. This can be caused by external forces (tight shoes or other external irritations) stressing the region initiating an increase in osteoblastic activity of the bony structures, over-‐pronation (which has the same effect as the external forces), and genetics. The patient may present with an avoidance during gait to put pressure through the 1st ray, over-‐pronation, weak musculature at the knee and/or hips, bony genetic abnormalities, and tight triceps surae.

Conservative treatment consists of ice for pain, orthotics, wider shoes, education on shoe tightness when lacing, and bunion pads. Surgery can be an option if the condition hasn’t responded to conservative options and/or the patient’s pain level is intolerable.

Figure 24. Hallux abductovalgus

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The Interphalangeal Joints There are a total of nine interphalangeal joints. This is accomplished because of the structural difference that exists between the lateral four digits and the first digit. The great toe contains only two phalanges, thus producing one interphalangeal joint. However, the lateral four digits have a total of three phalanges each. The proximal phalanx articulates with the middle phalanx via the proximal interphalangeal joint (Figure 25). Subsequently, the middle phalanx articulates with the distal phalanx through the distal interphalangeal joint. A general rule is that the more proximal phalanx consists of a convex head that meets up with the concave base of the more distal phalanx. Much like the metatarsophalangeal joints, each interphalangeal joint has a joint capsule that is reinforced by a pair of collateral ligaments. The interphalangeal joint structure allows the movement to occur in the sagittal plane, about the medial-‐lateral axis. This arrangement allows for flexion and extension. Neumann describes the amplitude of flexion as being greater than extension. It is also stated that the motion seems to be larger at the more proximal joint in comparison to the distal counterpart. The interphalangeal joints receive blood supply from the dorsal digital arteries and the plantar digital arteries. The plantar and dorsal digital nerves generate the innervation. The dorsal nerves originate from the superficial fibular nerve, while the plantar nerves come from the posterior tibial nerve. Tissue Layers of the Interphalangeal Joints – Superficial to Deep




o Dorsum of the Foot ! Tendons of Extensor Digitorum Longus

• Neurovasculature o Dorsal Digital Arteries o Dorsal Digital branches of the Deep Fibular Nerve o Lateral Dorsal Cutaneous Nerve

• Ligaments o Collateral Ligaments

Figure 25. PIP and DIP joints

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• Bones o Phalanges


• Ligaments o Plantar Ligaments

• Neurovasculature o Plantar Digital Arteries o Plantar Digital Nerves




o Third Layer ! Flexor Hallucis Longus Tendon ! Flexor Digitorum Longus Tendon ! Fibularis Longus Tendon ! Adductor Hallucis (Oblique and Transverse Heads)

o Fourth Layer ! Plantar Interossei ! Dorsal Interossei

• Fibrous Sheath of Flexor Tendons • Superficial Fascia



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Table 16. Joint Motions of the Interphalangeal Joints Joint Motion Primary Movers Secondary Movers

Flexion Flexor Hallucis Longus, Flexor Digitorum Longus, Flexor Digitorum Brevis

Flexor Hallucis Brevis, Abductor Hallucis, Quadratus Plantae

Extension Extensor Hallucis Longus, Extensor Digitorum Longus, Extensor Digitorum Brevis

Lumbricals

Biomechanics and Kinematics of the Interphalangeal Joints At the interphalangeal joints, more flexion than extension range of motion is available, and more motion exists at the PIP’s than the DIP’s. In open chain circumstances, the concave, distal articulating surface will roll and glide in the same direction on the convex, proximal articulating surface. In contrast, roll and glide will move in the opposite direction when the convex surface moves on the concave surface present in closed chain situations. The primary drivers for flexion at the interphalangeal joints are the flexor digitorum longus (for digits 2-‐5) and the flexor hallucis longus (for the great toe) muscles. These have the greatest cross-‐sectional area by far, even though their counterparts have a more direct line of pull. Assisting the flexor digitorum longus are the flexor digitorum brevis, lumbricals, and quadratus plantae. Helping the flexor hallucis longus are the flexor hallucis brevis and abductor hallucis. For extension, the extensor digitorum longus is the primary mover for digits 2-‐5. It is assisted by the extensor digitorum brevis, which has a better line of pull. Great toe extension is primarily accomplished by the extensor hallucis longus due to its biomechanically advantageous cross-‐sectional area. This is superior to the more biomechanically advantageous line of pull from the extensor hallucis brevis, which aids in great toe extension. Joint Configuration and Planes of Motion Each digit, with the exception of the 1st, consists of a proximal, middle, and distal phalanx, with an articulation between each. The articulation between the proximal and middle is called the proximal interphalangeal joint (or PIP), and between the middle and distal phalanges is the distal interphalangeal joint (or DIP). The great toe only has a proximal and distal phalanx, so their articulation is referred to as an interphalangeal joint (or IP). Each joint also has a synovial, joint capsule. The most proximal articulating surface is convex and the distal surface is concave. So, for example, the 2nd PIP consists of a convex proximal phalanx articulating with a concave middle phalanx. Along the same digit, the 2nd DIP will have a convex middle phalanx and concave distal phalanx. These joints are synovial, hinge joints. This means that they move in flexion and extension about the mediolateral axis.

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Table 17. Ligaments of the Interphalangeal Joints Ligament Attachments Function

Dorsal aponeurosis Wraps around the dorsum of the MTP, PIP, IP, and DIP’s of each joint.

Resist hyperflexion and hold the extensor tendons in place.

Cruciforms

Between the annular ligaments crossing from one side of the plantar surface of a phalanx to the other side.

Resists hyperextension and torsional movements

Annulars At the IP, PIP, and DIP’s of each joint running horizontally around the joint.

Resists medial and lateral movements at each joint.

Common Joint Pathologies of the Interphalangeal Joints Plantar fasciitis

Although this condition isn’t specific to this joint, the plantar fascia attaches to the anterior plantar surface of the phalanges, and is extremely common. Patients with plantar fasciitis will report pain in their heel (Figure 26), especially right along the anteroplantar surface of the foot, that is worse when they get up in the morning and after any prolonged period of rest. The pain will gradually get better as the day goes on, but can return with prolonged activities such as standing, walking, running, or jumping. This can lead to compensations presenting as decreased push off during terminal phases of gait. Plantar fasciitis can occur because of excessive pronation (due to either immobility at the ankle or weak ankle inverters), micro-‐trauma or inflammation near the point at which this tissue connects to the calcaneus, poor or old footwear, tight triceps surae, or high arches. With these patients, resistive tests should be negative however; active and passive range of motion of the great toe will reproduce their symptoms as will palpation at the calcaneal

insertion point. Another pathology associated with this condition is the formation of heel spurs. It is common in 30% of patients, but removal of the spur doesn’t correct the primary issue of tight plantar fascia.

Treatment of this condition includes stretching the triceps surae, ankle stabilizing muscle strengthening and neuromuscular re-‐education, foot intrinsic muscle strengthening and neuromuscular re-‐education, modalities as needed, rolling out or stretching the arch of the foot after prolonged periods of rest (like sitting or sleeping), rest, activity modification, patient education on footwear, orthotics, and addressing other imbalances or issues at the knee and hip as needed.

Figure 26. Plantar fasciitis

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Gout Gout occurs when an excess of uric acid builds up in the body and forms crystals.

The great toe is a common location for this to occur. Patients will present with sore, red, warm, stiff, or swollen joints that can be painful enough to arouse someone from sleep. This condition can be exacerbated by stress, alcohol, drugs, or other illnesses.

Gout is treated with NSAID’s, prescribed medications, or cortisone shots. Hammertoe

Hammertoe (Figure 27) is a condition affecting the 2nd, 3rd, or 4th toe. This can be caused by improper footwear, muscular imbalances, or an injury to the dorsal digital expansion.

Conservative treatment includes intrinsic and extrinsic foot exercises, stretching, pads or braces, and footwear changes and education. It can also be treated surgically, but may lead to hallux rigidus.

Figure 27. Hammertoe

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