CHAPTER 4:BODY ALIGNMENT, POSTURE, AND GAIT Gravitational EffectsPosture AnalysisPostural Changes During GrowthGravitational ForcesStabilization MechanismsThe Alexander TechniueThe Perry Techniue Stance and Motion PosturesStatic Stance and Sitting PosturesDynamic PosturesThe !al"ing Function#xamination o$ Gait%unning and &um'ingPractical Fluid MechanicsTypical Effects of Balance Defects#$$ects o$ (i'edism(ody Ty'e and (alance De$ects#tiology o$ Postural Faults(asic Physiologic %eactions to Postural Faults Gravitational EfectsImproper body alignment limits function, and thus it is a concern of everyone regardless of occupation, activities, environment, body type, sex, or age. To efectively overcome postural problems, therapy must be based upon mechanical principles. In the absence of gross pathology, postural alignment is a homeostatic mechanism that can bevoluntarily controlled to a signifcant extent by osseous adjustments, direct and refex muscle techniques, support when advisable, therapeutic exercise, and kinesthetic training.In the health sciences, body mechanics has often been separated fromthe physical examination. Because physicians have been poorly educated in biomechanics, most work that has been accomplished is to the credit of physical educators and a few biophysicists. Prior to recent decades, much of this had been met with indiference if not opposition from the medical profession.Posture Analysis It has long been felt in chiropractic that spinal subluxations will be refected in the erect posture and that spinal distortions result in the development of subluxation syndromes. Consequently, an array of diferent methods and instrumentation has been developed for this type of analytical approach such as plumb lines with foot positioning plates to allow for visual evaluation relative to gravitational norms, transparent grids, bubble levels, silhouettographs, posturometer devices to measure specifc degrees in attitude, multiple scale units to measure weight of each vertical half or quadrant of the body, and moire contourography. THE GAIT CYCLE The normal gait presents smoothness of function without any sign of impairment or afection of parts of the body. The normal walking cycleis considered to have two phases:(1) a stance phase, when the foot is in contact with theground; and (2) a swing phase, when the foot is moving forward in the air (Fig. 4.19).During normal walking, one leg is in the stance phase while the other isin the swing phase. Muscles must contract to counterbalance the forces of gravity, to ofer acceleration or deceleration to momentum forces, and to overcomethe resistance of the walking surface.The Stance Phase. About 60% of the walking cycle is used in the stance phase. Because the stance phase is the weight-bearing phase requiring the greatest stress, most problems will become apparent in its analysis. The stance phase is subdivided into:(1) heelstrike, (2) footfat, and (3) toe pushof.Midstance is that weight-bearing period between footfat to toeof. The duration of gait is usually measured from heelstrike to heelstrike, but any two identical points can be taken.The Swing Phase. This is subdivided into:(1) initial acceleration, (2) mid swing, and (3) fnal deceleration --depending upon the intent.The swing phase, about 40% of the gait cycle, begins with toeof and ends with heelstrike. Midswing represents the transition period between acceleration and decelerationExamination of Gait Every person has a gait, or manner of progressive locomotion, which ispeculiar to that individual. However, there are also various modes of walking peculiar to certain diseases which are important diagnostic clues. The range of movements in the lower extremities assists in recognizing specifc diseases and helps the doctor of chiropractic determine postural changes resulting from an unnatural gait. For instance, a shortened leg gives a characteristic limp. A stif knee causes the afected limb to swing outward while walking. Intermittent claudication or limping is observed in chronic peripheral vascular diseases such as endarteritis because muscular activity requires moreblood than muscular inactivity.As the walking gait is the most fundamental form of dynamic posture, it should form the basis of holistic biomechanical analysis. In health, most locomotive adjustments are conducted at an unconscious level. This is not true with the patient sufering a neuromusculoskeletal disability afecting gait. Every motion may require a frustrating conscious efort such as that taken by a healthy person stepping into a canoe where the support is unfamiliar.Although children emulate adult gait in many respects, there are diferences that must be considered in analyzing a pathologic or functionally impaired gait during childhood. Foley and associates, utilizing a TV-computer system of data gathering and analysis, found that joint-angle ranges were the same in children as those of adults.5(155)4 However, accelerations, velocities, and linear displacements were consistently larger for children aged from 6 to 13 years (mean value 10.2) than were adult values.SITTING AND ASCENT During examination, have the subject sit in a chair, arise, and then walk across the room if you have not had an opportunity to witness this previously. The chair should be one that gives frm sitting supportand provides for 90 fexion of the knees and hips.While the patient is sitting, note from the front the patient's sitting balance, levelness of ears, shoulders, and pelvis. From the side, note head, shoulder, and pelvic carriage. Observe how the patient rises from the chair to the standing position. Note the needed base of support: how far the knees are apart and how far the forward foot is from the back foot. If the chair has arms, note the degree the hands are used from sitting to standing to assist weak knees, weak hip extensors, or to maintain stability, balance, and coordination.NORMAL STANCE AND SWING PHASES Noting a gait deformity and in what phase it occurs is most helpful to diagnosis. Many subtle but signifcant points are frequently missed in the fully clothed patient, thus the patient should be minimally clothedand examined in a private environment. Immediately after analysis, make a graphic or mental record of your impressions of the subject's gait. Osler, the great diagnostician, warned that more can be learned by observing the body in dynamic action than can be learned upon the autopsy table when it is too late to help.During normal ambulation, the normal range of motion at the ankle isfrom 20 plantar fexion to 15 dorsifexion. The knee moves 65 from fexion to extension. At the hip, about 6 of adduction occurs and a 45 range is necessary from fexion to extension.After the walking sequence has been initiated, the movements are normally continued in a rhythmic manner solely by refex actions. Thestretch refex of the antagonistic extensor muscles is refexly inhibited as the fexors of the hip, knee, and ankle are stretched. Walking actions are maintained by the refexive interplay of muscles acting around the joints in motion (Fig. 4.24).During the stance phase, the heelstrike to footfat, footfat to midstance, midstance to heelof, heelof to toeof, toeof to midswing, and midswing to heelstrike actions should be analyzed. During the swing phase, which is only about a third of the cycle, the acceleration to midswing and midswing to deceleration actions should be analyzed.HEELSTRIKEInspection. At heelstrike, the ankle is between dorsifexion and plantar fexion, the knee is fully extended, the hip fexes to about 25, and the head and trunk are vertical. The right arm is posterior to the midline of the body with the elbow extended, and the left arm is anterior to the midline with the elbow partially fexed. The pelvis is slightly rotated anteriorly, the knee is extended, and the leg is vertically aligned with the pelvis. The foot is near a right angle to the leg on the side of heelstrike, and the plantar surface of the forefoot is visible from the front (Fig. 4.25).Mechanisms. The reactive force of the ground tends to plantar fex the foot so that a large surface contacts the ground, to fex the knee, and to drive the hip into greater fexion. This reactive force is checked by extensor action of the joints involved; ie, contraction of the ankle dorsifexors, eccentric quadricep contraction at the knee, and contraction of the gluteus maximus and hamstrings at the hip. These mechanisms prevent fexion collapse under body weight and absorb the impact jar at heelstrike. There is also some contraction of the posterior hamstrings at heelstrike, but this is considered only to prevent hyperextension of the knee.Joint Reaction. At heelstrike, it has been calculated that the magnitude of the joint reaction at the foot is 5.8 times body weight for a heavy, energetically walking male. It is 2.3 times body weight for an average female walking slowly. For both male and female, the maximum joint reaction at the knee during walking is about four times body weight. The posterior cruciate ligaments carry more than twice the shearing forces carried by the anterior cruciates.FOOTFLATInspection. In weight bearing, the pelvis rotates on its vertical axis, the femur rotates on the pelvis, and the tibia rotates laterally on the femur.Mechanisms. During footfat, maximum stabilization of the foot occurs during stance when body weight is directly above the foot. Forward momentum eliminates the need for active hip and ankle fexion or extensor stabilization, but there is some knee fexion by quadricep contraction. When body weight is placed on the stance side,the plantar fexors of the foot contract to counterbalance the reactive force of the walking surface which forces the foot into dorsifexion up to 15 at heelof, and the adductors of the hip contract to counterbalance the pelvic adduction resulting from pelvic tilt.MIDSTANCEInspection. At midstance, the head and trunk are vertical with the arms near the midline of the body and at an equal distance from the body. The elbows are partially fexed. On the weight-bearing side, the pelvis is rotated slightly anterior, the knee is in slight fexion, the leg isin slight lateral rotation at the hip, and the ankle is in slight dorsifexion. There is a downward pelvic tilt on the contralateral side (Fig. 4.26).Mechanisms. Following full vertical weight bearing, the line of gravity moves forward on the stabilized plantar surface to produce a reactive force which contributes to ankle, knee, and hip extension. Hipextension reaches about 15 at the time of heelof. This takes place without any active extensor muscle action, but some stabilization efect occurs by the iliopsoas. During this process, the gravity line falls anterior to the knee so that quadriceps action is no longer necessary. The ground reaction moves from the midfoot to the forefoot as toeof approaches which increases the moment of dorsifexion. In reaction, plantar fexion contraction peaks at heelof to drive the body forward. While this tends to extend the knee, full extension is restricted by the gastrocnemius --an ankle and knee fexor.Energy Absorption. During gait, peak activity of the joints of the lower extremity is reached during the period of double support. At thisperiod, the knee muscles are absorbing energy while the other joints are producing energy. As the hamstring group and gastrocnemius are two-joint muscles, much of this energy can be transferred to produce energy at other joints.Compensation. When the power output of one segment exceeds the power required, the surplus energy must be absorbed by other segments. Likewise, when the power requirement of one segment exceeds muscle output, the energy necessary must come from other segments.Efect of Shoe Lift. Although unsymmetrical lower extremity length has long been known to have adverse efects in the spine, only recentlyhas its efects on contributing to depleting the body's energy stores been measured. Delacerda and Wikof have shown that the equalization of leg length by a shoe lift equalized the time durations for the four phases of gait and decreased the kinetic energy of the lower extremity segments for both legs in spite of the diference in segmental masses of the legs bilaterally. (158)PUSHOFFInspection. On the side of pushof, the arm is anterior to the midline of the body and the elbow is partially fexed. On the contralateral side, the arm is posterior, the elbow is slightly extended. Both arms are equally distant from the body. On the side of pushof, the femur is slightly rotated laterally at the hip, the knee is slightly fexed, the ankle is plantar fexed, and the toes are hyperextended at the metatarsophalangeal joint. The plantar surface of the heel and midfoot should become visible from the posterior during pushof (Fig. 4.27).Mechanisms. The later part of stance occurs between heelof and toeof and provides the major portion of forward and vertical propulsion force. The hip adductors and iliopsoas begin to contract in anticipation of the swing phase, but most action occurs at the ankle and knee. The ankle changes from about 15 dorsifexion at heelof to about 35 plantar fexion at toeof, and the extended knee fexes to about 40 as the quadriceps contract. At toeof, the segments begin to reverse the lateral rotation attained during footfat, and this medial rotation of the pelvis, thigh, and leg continues to 2035, depending on walking speed, until the next footfat is reached. Once the toes leave the ground, hip and calf muscles relax.ACCELERATIONInspection. The period of acceleration of the advancing leg occurs during the frst part of the swing phase when the limb is between toeof and midswing. The swing phase involves almost simultaneous hip fexion, knee fexion, ankle dorsifexion, and usually a concomitantforward swing of the hip that rotates the pelvis contralaterally to somedegree.Mechanisms. The primary forces are generated by the hip fexors and ankle dorsifexors. Hip fexion is governed by the tensor fasciae latae, the pectineus, and the sartorius. The most powerful hip fexor, the iliopsoas, and the adductor magnus are not active during swing, according to electromyographic evaluations. Knee fexion is aided by sartorius contraction, gravity, and passive pull of the posterior hamstrings. The fexion of the knee after toeof is passive while the thigh accelerates forward from action by the hip fexors. As the hip and knee continue to fex and the ankle dorsifexes, the leg "shortens" so that it can clear the ground.MIDSWING AND DECELERATIONInspection. The head and trunk are vertical, and both arms are nearthe midline of the body and held an equal distance from the body. On the weight-bearing side, the pelvis is rotated slightly anteriorly and tilted downward, the hip and knee are fexed, the femur is rotated slightly medial at the hip, the leg is vertically aligned with the pelvis, and the foot is at a right angle to the leg and slightly everted (Fig. 4.28).Mechanisms. At heelstrike, the ankle is held in its neutral position by its dorsifexors, especially the anterior crural muscles, the knee rapidly moves from fexion to full extension by hamstring contraction, and this hamstring contraction also slows hip fexion. During the swing phase, there is a ballistic movement of hip fexion where the thigh is frst accelerated by the hip fexors at the beginning of swing and then decelerated by the hip extensors.LATERAL OBSERVATION From the lateral note rhythm, symmetry, speed, and stride lengths of cadence. Vertical excursion is best viewed from the side. Check if the duration of the stance phase is the same bilaterally. As the patient walks, note all deviations from normal gait. Normally, the head and trunk are vertical, stride length is even, and the arms swing freely andalternate with the leg swing.Note the foot at heelstrike and pushof. The foot is about at a right angle to the leg and the knee is extended but not locked at heelstrike. At pushof, the foot is frmly fexed and the toes are hyperextended. The foot easily clears the foor during the swing phase of the gait.Displacement. The trunk should be vertical at stance. Observe the degree of lurch during fexion, extension, and during the swing phase. Note degree of hip, knee, and ankle fexion. If the head is carried far forward, seek further evidence of atlanto-occipital fxation, subluxation, costoclavicular or neurovascular syndrome, upper dorsal lesion, or shoulder disorder. These malfunctions would also be suspectif the head were titled to one side, but lateral carriage is found more commonly in torticollis, in visual defects, and in primary or secondaryscoliosis.Pathologic Postures. If pain is present, determine where and when it is greatest. Check for trunk fxation in fexion or extension. Fixed lordotic and kyphotic spines will be evident during both stance and swing, but posterior pelvic tilts are difcult to observe. Shoulders drooping forward may be an indication of cardiac dysfunction, lung or pleural pathology, depression, or a dorsal lesion. Diabetics and those sufering from cardiorenal disorders often have pot bellies. Due to the lack of tone in the abdominal musculature, the viscera sag downward which results in organ malposition and disturbed function contributing to the problem.ANTERIOR-POSTERIOR OBSERVATION From the front and rear, note rhythm, symmetry, and speed of cadence. Lateral motions are best viewed from the front or rear. As thebody advances, note smoothness of the body's vertical oscillation. Pathology may express itself in increased vertical oscillation and disrupt the normally smooth pattern. Normally, the pelvis is centrally positioned over the line of progression at toeof and begins its movement toward the side of the weight-bearing limb.Pelvic Displacement. Note the degree of pelvic tilt and drop on each side. This is more easily noted by watching the top horizontal line of the underwear. A lateral shift of the pelvis and hip of about one inch to the weight-bearing side is normal to center the weight over the hip. Maximum pelvic tilt is usually reached just after midstance. Its degreeis normally determined by stride width, which corresponds to the lateral shear forces acting on the pelvis, and walking speed, which determines how long these shear forces are acting on the body. Lateralshifting is accentuated in gluteus medius weakness and should be noted. A gait exhibiting bending to one side may be the result of a pericardial or pleural friction rub, a sacroiliac lesion, shoulder condition, afection of the brachial plexus, or lesion in the upper dorsal section of the spine. On the other hand, a ram-rod gait is a signof a thoracic lesion, sacralization, or spasm of the lumbar paravertebral musculature --all of which may or not be associated with an abnormal lumbar curve. A fxed pelvic tilt or elevation will not change from stance to swing. The pelvis is normally level at heel contact, drops to its maximum on the side approaching toeof during double-support, then returns to a level position shortly after toeof and remains there until heel-strike. As speed increases, the degree of drop increases on the side in the swing phase.Base Width. Check the walking base width for broadness, stability, and consistency (Fig. 4.21, right). From heel to heel, base width is normally not more than from 2 to 4 inches. If wider, dizziness, unsteadiness from a cerebellar problem, or numbness of a foot's plantar surface may be a cause for the wider base. An abnormally decreased base usually produces a crossover "scissor" action after midswing.Limp. Any articular malfunction from the spine to the foot may result in a limp. Muscular weakness or spasm, fascial contraction, fracture, a torn ligament or tendon, bone disease, or a neurologic afectation may be cause for a limp. Generally, an uncomplicated limp can be traced to a knee, ankle, or foot dysfunction or deformity, a hip disorder, or a sacroiliac or lumbar lesion. A female gait exhibiting rigidbuttocks is a sign of a uterus retrofexed or prolapsed, or of a lumbosacral lesion.DIAGNOSTIC STANCE AND SWING CLUESHeelstrike. Inability of a foot to heelstrike is an indication of a heel spur and associated bursitis or a blister. Failure of the knee to fully extend during heelstrike is a sign of weak quadriceps or a fexion fusion of the knee. A harsh heelstrike, usually associated with knee hyperextension, is a frequent sign of weak hamstrings.Footfat. When the foot slaps down sharply after heelstrike, weak dorsifexors should be suspect.Midstance. Fused ankles will prevent a midstance fat foot. Weak quadriceps display themselves in excessive fexion and poor knee stability during mid-stance. A midstance forward lurch of the hip is a typical indication of a weak gluteus medius, while a midstance backward lurch is a sign of a weak gluteus maximus.Pushof and Swing. If the patient must rotate the pelvis severely anterior to provide a thrust for the leg, the cause is most likely weak quadriceps. If the hip is fexed excessively to bend the knee and thus prevent the toe from scraping the foor as in a steppage gait, weak ankle dorsifexors are the usual cause. Failure to hyperextend the foot during pushof is a sign of arthrosis. Pushing of with the lateral side of the front of the foot is usually seen in disorders involving the great toe. A fat-footed calcaneal gait during pushof is symptomatic of weak gastrocnemius, soleus, and fexor hallucis longis muscles. The foot willhave trouble clearing the foor if the ankle dorsifexors are weak or the knee is unable to fex properly.ANTALGIC GAITSGuarded Limps. A limp may be a sign of disease, malfunction, or both. It may also be in compensation to another condition such as a sprained ankle, injured knee, old fracture malunion or hip surgery. However, the majority of limps seen are those desribed as "guarded" limps. Guarded limps frequently point to specifc musculoskeletal disorders. These limps are the result of the patient walking in a manner that protects or relieves stress upon an area that would otherwise be uncomfortable or painful. The term "antalgic position" is that static posture assumed by the patient to produce the same pain diminishing efect as does a guarded gait.Midspinal and Bilateral Spinal Pain. When pain is in the midline of the spine, the gait pattern is guarded, symmetrical, slow, with a short stride and restricted trunk rotation and pelvic tilt. If paraspinal muscle spasm is present, the patient will tend to lean backward throughout the gait in compensation. However, if the irritation is located at the posterior aspect of the spinal column (eg, articular facets), the patient will tend to lean forward throughout gait in an attempt to gain relief by reducing weight on the sensitive area. Walkingon the toes, as if walking on eggs, is often seen in cases of lumbosacral or cervical lesions to reduce jar. To avoid jarring any sensitive joint, the heel strike is usually eliminated and the length of stride is shortened by reducing the swing phase.Unilateral Spinal Pain. Walking in a stooped position with one hand supporting the back is a frequent sign seen in a lumbar lesion. Duringboth stance and swing in mild or moderate irritations, the trunk usually leans toward the afected side in compensation to muscle splinting. However, in pronounced intervertebral disc or sacroiliac lesions, the lean is usually away from the site of irritation to reduce pressure.Hip Pain. While the hip joint of one extremity is in the stance phase and acts as the fulcum for rotation, the other hip in the swing phase rotates about 40 forward. This normal hip rotation is not seen in patients sufering a stif or painful hip. When a hip is painful, the gait is asymmetrical, the base is widened during swing, the stance phase is reduced on the afected side and made longer on the unafected side, the trunk is thrown forward during stance to shift the center of mass, and the afected hip is lifted so the limb will clear the foor. The afected hip is quite fxed in fexion, abduction, and rotated laterally toreduce joint tension. As a consequence to the hip fexion, the knee andankle fex. Keep in mind the cyclic load on the hip during gait (Fig. 4.29).Knee Pain. If a knee joint is efused, with or without pain, 25 fexion ofers the largest capsule volume, and thus the least tension. This fexion is compensated by ankle plantar fexion and an absent heelstrike, so that the patient will walk on the toes of the afected side.This guarded gait minimizes quadriceps function and thus reduces knee compression.Ankle Pain. In any painful disorder of the ankle, ankle motion will beguarded and the most comfortable position will be assumed. There is little, if any, plantar fexion during footfat or heelstrike, or dorsifexionduring heel-of. This will be compensated for by an exaggerated knee fexion after heelof and a restricted heel rise before toeof. The patient will reduce his base and shift his trunk so that more weight falls directly over the joint during weight bearing.Common Stance-Phase Problems. Most stance phase problems are the result of pain and characterized by an antalgic gait wherein the patient spends as little time on the afected extremity as possible. Gaitpatterns vary according to the type and location of the disorder present. A shoe problem should not be overlooked, as it is one of the more common causes. Pain in a foot during midstance may be caused by corns, calluses from a fallen transverse arch, rigid pes planus, a plantar wart, bunion, subtalar arthritis, or poor-ftting shoes. Heel-strike will be eliminated, and toe walking will be seen, if a lesion is present in the heel or posterior aspect of the foot. Lesions of the forefoot such as metatarsal or phaangeal disorders are characterized by heel walking, reduced pushof, and an exaggerated forward hip thrust and knee fexion in compensation. Sharp pain on pushof is often caused by corns between the toes or metatarsal callosities. In longitudinal arch disorders, weight will be borne on the lateral plantarsurface during weight bearing. If chronic, excessive wear on the lateralsole of the shoe will be noted.Running and Jumping The mechanics of running are similar to those of walking in several respects. Both walking and running require that:(1) weight be projected forward and the legs are carried alternately under the body for brief periods of support, and (2) the weight-bearing limb provides the propulsive action after the center of body weight has passed over it. Walking becomes a running gait at that point in acceleration when a period of nonsupport appears. During the phase of nonsupport where there is no surface friction, the body can be considered a missile.Jumping is essentially the act of propelling the body into the air via rapid leg extension. It is usually considered in three phases: takeof, fight, and landing. Jumping is governed by the same principles that govern missiles. Thus, the motions made during fight have little infuence on direction, height, or distance. Their main purpose is to prepare the body for Impaired corrective responses to postural perturbations of the arm in individuals with subacute strokeBackgroundStroke is known to alter muscle stretch responses following a perturbation, but little is known about the behavioural consequences of these altered feedback responses. Characterizing impairments in people with stroke in their interactions with the external environment may lead tobetter long term outcomes. This information can inform therapists about rehabilitation targets and help subects with stroke avoid inury when moving in the world.Methods!n this study, we developed a postural perturbation task to quantity upper limb function of subects with subacute stroke "n # $%& and non'disabled controls "n # ()& to make rapid corrective responses with the arm. Subects were instructed to maintain their hand at a target before and after a mechanical load was applied to the limb. *isual feedback of the hand was removed for half of the trials at perturbation onset. + number of parameters quantified subect performance, and impairment in performance was defined as outside the ,-th percentile performance of control subects.Results!ndividual subects with stroke showed increased postural instability ")).&, delayed motor responses "(,.&, delayed returns towards the spatial target "(,.&, and greater endpoint errors "().&. Several subects also showed impairments in the temporal coordination of the elbow and shoulder oints when responding to the perturbation ")(.&. !nterestingly, impairments in task parameters were often found for both arms of individual subects with stroke "up to -%. for return time&. *isual feedback did not improve performance on task parameters except for decreasing endpoint error for all subects. Significant correlations between task performance and clinical measures were dependent on the arm assessed.ConclusionsThis study used a simple postural perturbation task to highlight that subects with stroke commonly have difficulties responding to mechanical disturbances that may have important implications for their ability to perform daily activities.Keywords: Stroke, /roprioception, +ssessment, /erturbation, 0pper limb, 1obotics