Gross Anatomy: Bones

patellar surface

intercondylar eminence

Gross Anatomy: Skeletal Structure

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Gross Anatomy: Articular Surfaces

Gross Anatomy: Menisci

Fibrocartilaginous structures

Attach to tibia in intercondylar region

Transverse ligament connects the

anterior horns of each menisci

Vascular periphery (2-3 mm)

Medial meniscus

Oval-shaped

Attached to MCL

Thinner , less mobile

Lateral meniscus

Circular

Thicker, more mobile

Gross Anatomy: Synovial Membrane

MM

PCL

ACL

LM

Does not invest cruciate ligaments!

Bursae:

•Suprapatellar

•Subpopliteal

•Prepatellar

•Subcutaneous

infrapatellar

•Deep infrapatellar

Gross Anatomy: Ligaments

Medial Collateral (MCL)

Lateral Collateral (LCL)

Anterior Cruciate (ACL)

Posterior Cruciate (PCL)

Meniscofemoral (MFL) Meniscofemoralligament

Gross Anatomy: Muscles Thigh

Quadriceps femoris – VL, VM, VI, RF

Sartorius

Gracilis

Hamstrings – BF, SM, ST

IT band – GM, TFL

Leg Gastrocnemius

Plantaris

Popliteus

(Pes anserinus)

Gross Anatomy: Popliteal Fossa

1. Semitendinosus

2. Biceps femoris

3. Semimembranosus

4. Sciatic nerve

5. Popliteal vein

6. Popliteal artery

Tibial n. Common peroneal n.

Gross Anatomy: Vasculature Patellar Plexus

Anastomoses of descending branch of lateral circumflex femoral a., anterior tibial recurrent a., and genicular branches

Popliteal Artery

Med./Lat. Superior Genicular

Middle Genicular – enters capsule post. to supply ligaments and synovium

Med./Lat. Inferior Genicular

Circumflex Fibular

Gross Anatomy: Nerve Supply Sciatic nerve

Tibial n.

Common peroneal n.

Wraps around head of fibula

Saphenous branches

Run deep to pes anserinus

Patellar Dislocation Predisposition

Genu valgum

Overweight

Patellar hypermobility

Weak quadriceps

Mechanisms Direct contact to

medial side

External tibial rotation with forceful quadriceps contraction

Patellar Dislocation

Vastus medialis strain

Tearing of medial patellar retinaculum

Hemarthrosis

Reduces with extension

Patellar Dislocation: Diagnosis Obvious if not yet

reduced

Patellar hypermobility/ apprehension test

X-ray/MRI only necessary to rule out osteochondral fractures, other associated injuries

Patellar Dislocation: Treatment Knee extension

Aspiration to relieve discomfort and check for fat in blood

Surgery unnecessary unless osteochondral fracture or complete rupture of MPFL

Crutches, PRICES

Rehabilitation focusing on vastus medialis

Meniscal Tears Shear force from femur

Acute or degenerative

Athletes, elderly, overweight

Vascular zone?

Horizontal Within substance

Longitudinal Bucket handle – ACL risk

Radial or vertical Parrots beak

Medial Meniscus Tear Tears easier than lateral

due to certain traits

Squatting

Internal rotation of tibia with knee flexed

Member of “unhappy triad” Medial meniscus

MCL

ACL

Medial Meniscus: Diagnosis MRI

Low-signal intensity (black triangle ) = normal

White interruption = lesion

Arthroscopy as last resort

Lateral Meniscus Tear Lower incidence

Often more painful

More likely to incur radial or parrots beak

Not rare for anterior horn

Discoid meniscus

Wrisberg variety

Congenital (1.5-3%)

MM only 0.1 – 0.3%

femur

Discoid meniscus

MCL: Diagnosis: Examination Abduction stress test

First at 30

Again at full extension Rule out PCL tear

Anterior drawer test with external rotation of tibia Hip flexed 45

Knee flexed 90

Tibia rotated 30 ext.

Anterior rotation of medial tibial condyle

MCL: Diagnosis: Imaging X-ray

Only useful for young patients to differentiate from epiphyseal fracture

Taken at 20-30 flexion Enlarged joint space = tear

MRI Coronal scan Normal MCL looks thin,

taut, low-signal Grade I: indistinct MCL

(edema) Grade II: thicker, looser Grade III: severe edema

MCL: Treatment Surgery necessary for

compound injury

Crutches + PRICES + rehab for Grade I, IIonly if isolated

Grade III tears may require surgical repair, but immobilization can be effective if isolated(rare) 3-4 months recovery

Surgery Open incision

Midsubstance ruptures sutured

Tear from bone repaired with suture anchors

Lateral Collateral Ligament Courses slightly posterior

Sprained least frequently

Adduction force rare

BF, popliteus, IT tract

Flexed knee = isolated tear

Anteromedial blow hyperextension/ postero-lateral corner injury

Risk to common peroneal nerve

Foot drop, sensation loss

LCL: Diagnosis: Examination Adduction stress test

At 30, then full extension

Ext. rotation recurvatum Lift legs by great toes Recurvatum + ext rotation +

varus = PL corner injury

Posterolateral drawer test Tibia externally rotated,

posterior force applied

Reverse pivot shift test Knee 90, tibia ext. rotated With valgus, slowly extended

Temporary posterior subluxation of lateral tibial condyle around 30

Forcibly reduces with extension

LCL: Imaging and Treatment MRI

Coronal oblique scan

Sagittal scan to rule out fibular fracture, avulsion

Tear looks less taut or discontinuous – no thickening

Treatment Similar to MCL

Grade III usually requires surgery

Anterior Cruciate Ligament Most common knee injury

among athletes AM fibers taut in flexion

Check anterior displacement

PL fibers taut in extension Check rotation

Hyperextension, internal rotation – rarely isolated injury from contact force

“unhappy triad” May tear from tibia (3-10%),

from femur (7-20%), or in midportion (70%) Proximal end receives branch

from middle genicular a.

Internal rotation of right knee

(LEFT KNEE)

ACL: Diagnosis: Examination History, large hemarthrosis Autonomic symptoms Anterior drawer test

Tibia neutral, pull ant. NOT RELIABLE BY ITSELF

Lachman test Knee only flexed 15-20

Pivot shift/jerk test Start in extension, tibia

internally rotated, valgus Slowly flex, lateral tibial

condyle temporarily subluxates anteriorly ~30

Reduces with further ext. Jerk test opposite (90o)

ACL: Diagnosis: Imaging

X-ray Segond fracture of

lateral tibial condyle

ACL tear with it 75-100%

Tibial spine avulsion in young patients

MRI – 95% accuracy All 3 planes in full

extension

Edema/hemorrhage often obscures ACL

Normal ACL Torn ACL

ACL: Treatment Extrasynovial, heals

poorly

Partial, isolated tears may be treated with PRICES, rehab, bracing of slightly flexed knee

Most tears, athletes will require reconstruction

Posterior Cruciate Ligament Broader, longer, stronger

PM and AL fiber bundles

Receives better vasc. from MGA, synovial membrane

Checks post. displacement

Tears much less frequently

Only in isolation when “dashboard knee” injury

Hyperextension in sports, especially with side force

Falling to ground with foot plantar flexed

Posterior view

Anterior view

Medial femoral condyle

PCL: Diagnosis Posterior drawer test

Neutral start vital!

Gravity or sag test

Hips at 45 or 90, compare tibialtuberosities for sag

Abduction/adduction stress test at full extension

X-ray to confirm sag test

MRI shows lower-signal intensity for intact PCL compared to ACL due to its fiber organization Take on all 3 axes, but best

is sagittal oblique

negative positive

Cruciate Ligament Reconstruction

Complete excision followed by graft insertion

Allograft

Autograft

Patellar, quadriceps, hamstrings, calcaneus tendons used

Undergoes biological modifications: inflamed, necrotic revascularization extrinsic fibroblasts repopulate

ACL Reconstruction Autografts

B-PT-B

Quadruple hamstrings Semitendinosus, gracilis

Only replace AM

Double-Bundle Provides rotational

stability

BTB as AM bundle Fixed at 20

ST as PL bundle Fixed at 90

PCL Reconstruction Usually allograft –

calcaneus tendon

Incorporates well with long-term stability

BTB and ST often too short

Can achieve full function with reconstruction of just AL bundle

A. Low-power view cross section of PCL 11 years after calcaneus tendon graft. B. High-power

A B

Future of Reconstruction Goals:

Improve recovery time

Improve remodeling of insertion sites

Improve nervous and vascular restoration

With biological manufacture of: Growth factors, cytokines

Antibiotics

Techniques: Gene therapy – viral/non-viral vector delivers specific gene

Tissue engineering – mesenchymal stem cells