Locomotor Biomechanics and Pathomecanics a Review

8/12/2019 Locomotor Biomechanics and Pathomecanics a Review

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01964011/87/09010003 02.00/0THEJOURNALF ORTHOPAEDICND SPORTSHYSICALHERAPYCopyright 987 by The Orthopaedicand Sports PhysicalTherapy Sectionsof theAmericanPhysical Therapy Association

Locomotor Biomechanics andPathomechanics A ReviewLARRY P. BROWN, MA PT, ATC, PATRICIA YAVORSKY, BS, P T t

This review is intended to provide a working knowledge of clinical anatomy andarthrokinematics of the foot and ankle. Primary functions of the foot the gait cycleand pathomechanics will also be d iscussed. Emphasis is placed on basicbiomechanical considerations which form the basis for both static and dynamicevaluations. Also presented are some of the most commonly seen osseousdeformities contributing to pathomechanics.

Locomotion is the process or ability by whichman moves himself from one geographic locationto another.'' Biomechanics defined at face valueis made up of two roots, bio and mechanic^.^Bio indicates a relationship to life, living tissue,or organisms.24 Mechanics is a physical sciencedealing with the state of bodies and the action offorces.20Therefore, locomotor biomechanics per-tains to the study of forces and the effects ofthose forces on and within the human body whilemoving from one position to another.Familiarity with the biomechanics of walking isa prerequisite for an appreciation of the biome-chanics of running since the same basic mechan-ics are present in both gaits. To further appreciatethe various types of pathomechanics seen in therunner, a good working knowledge of normallocomotor biomechanics is necessary. This allowsthe practitioner to identify abnormal biomechanicspresent during running so that treatment can bebased on a firm scientific basis rather than on anempirical one.14 To support this statement, thisarticle will include discussions on basic arthroki-nematics of the foot and ankle, primary functionsof the foot, review of the gait cycles, and patho-mechanics.ArthrokinematicsAnkle

The ankle joint is composed of three joints: thetibiotalar, fibulotalar, and tibiofibular. The con-* Director. Palo Alto Physical Therapy and Sports Injury Center. 913EmersonStreet, PaloAlto. CA 94301.Director,La Jolla SportsTherapy

gruency of the ankle mortise is maintained by thestrong ligamentous system, the capsule, the in-terosseous ligament, and the various tendons andretinacula about the joint. Functioning primarily asa hinge joint, it allows for motion in 1 f freedom,the sagittal plane. These movements are typicallyreferred to dorsiflexion and plantarflexion. How-ever, the axis of rotation is described as passinglaterally through the talus and slightly inferopos-teriorly on the transverse plane.'* Since this axisis not exactly perpendicular to the sagittal plane,slight motions of abduction and eversion accom-pany dorsiflexion, and adduction and inversionaccompany plantarflexion. Most authors reportthat functional range of motion for the ankle is onthe order of 10-20' of dorsiflexion and 20-30' ofplantarf le~ion.~-'~~'~hen these movements be-come extreme, the subtalar joint and midtarsaljoints contribute to the range of motion of theankle joint.Subtalar Joint

The subtalar joint is the articulation betweenthe inferior surface of the talus and the superiorsurface of the calcaneus. This articulation occursat two separate articular facets, a posterior facetwhere the inferior concave surface of the talusrests on the superior convex surface of the cal-caneus, and an anterior facet with a convex talarfacet fitting into the concave calcaneal surface.These facet surfaces are united by powerful liga-ments that withstand the stress of locomotion.The reported axis of rotation is 41-45' from thehorizontal in the sagittal plane and 16-23' medi-ally, when measured from a longitudinal axis pass-


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BROWN ND Y VORSKY JOSPT Vol. 9 No. 1ing through the midcalcaneus in the transverseplane.4~9~'0~'2~15his oblique single axis is orientedfrom a posterior, lateral, inferior position, to ananterior, medial, superior position.13 The obliqueorientation of the axis causes it to traverse thethree cardinal planes, thus movement about thisaxis will occur in all three planes. The term usedto describe this type of movement is triplanarmotion. Manter15describes the overall movementof the subtalar joint as a combination of eversion,abduction, and slight dorsiflexion of the foot. Thiscombined triplanar movement is simply termedpronation. The combined movements of inver-sion, adduction, and slight plantarflexion aretermed supination. The amount of subtalar jointrange of motion reported is controversial; how-ever, most authors agree that the amount ofinversion as a component of supination is signifi-cantly greater than eversion as a component ofpronation when the foot is free.l4 The -normalfunctional range of motion seen in walking isbetween 6 and 10 of motion equally divided bya neutral position of the subtalar joint. The neutralsubtalar position as described by Root et aI.l7 isthat position from which the subtalar joint can bemaximally pronated and supinated, or when thesubtalar joint is neither pronated nor supinated.Midtarsal Joint

The midtarsal joint or transverse tarsal jointconsists of the talonavicular oint medially and thecalcaneocuboid joint laterally. Two separate ro-tational movements with distinct axes are de-scribed by Manter.15 Both axes are positionedobliquely to the cardinal planes; thus, they exhibittriplanar motion. The longitudinal axis of the mid-tarsal joint is directed anteriorly and superiorly15 from the horizontal plane, and medially di-rected 9 from the longitudinal plane. It allowspivotal movements of the cuboid on the calca-neus. The axis passes between the first andsecond rays, and allows motion of inversionlad-duction and eversion/abduction of the cuboid. Theoblique axis of the midtarsal joint is directed an-teriorly and superiorly 52 from the horizontalplane, and medially 57 from the longitudinalplane. The major actions about this axis are dor-siflexion/abduction, and plantarflexion adductionof the forefoot.Though the description of the midtarsal jointappears complex, the biomechanical function canbe greatly simplified by recognizing that motionperpendicular to the two axes may be indepen-

dent of each other, but both depend on the posi-tion of the subtalar joint. When the calcaneus isin an everted position, the subtalar joint is pron-ated and the planes of the axes between thetalonavicular and calcaneocuboid joints becomeparallel. This results in increased midtarsal jointmotion by unlocking the j ~ i n t . ' ~ ~ * ~onversely,when the calcaneus is inverted, the axes are nolonger parallel, and there is decreased motion ofthe midtarsal joint due to the convergence of theaxes. This convergence locks the bones of themidtarsal joint creating a rigid forefoot. The mo-bility created during rearfoot pronation and therigidity created during supination play a major rolein the primary functions of the foot.Other Functional Joints

The first ray is a functional metatarsal unit con-sisting of the first metatarsal and the first cunei-form bones. The first metatarsallfirst cuneiformjoint, and the first cuneiform navicular joint movetogether about a common axis of m ~ t i o n . ~heaxis passes anteriorly, laterally, and plantarlythrough the foot at a 45 angle from the frontaland sagittal planes. This axis produces the tri-planar motions of dorsiflexion/inversion, and plan-tarflexion/eversion.The second, third, and fourth r&s are formedby the articulations of the metatarsals with theappropriate cuneiforms. Each of these rays ap-pears to exhibit pure sagittal plane motion.The fifth ray consists of the fifth metatarsal only.The axis of motion lies at an angle of approxi-mately 20 from the transverse plane and 35from the sagittal plane. Therefore, t has a triplanaraxis allowing movement in the directions of supi-nation and pronation.The first metatarsophalangeal oint consists ofthe articular surface of the first metatarsal headand the base of the proximal phalanx of the hallux.It has two distinct axes of motion, a transverseaxis and a vertical axis. Pure plantarflexion anddorsiflexion are provided by the transverse planeand pureadduction/abduction are provided by thevertical plane.'*PRIM RY FUNCTIONS OF THE FOOTDURING LOCOMOTION

The joints of the foot perform two primary func-tions during the stance phase of gait; they allowthe foot to interface with the ground and theyprovide a base over which the body can be pro-


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JOSPTJuly 1987 LOCOMOTOR BIOMECHANICS AND PATHOMECHANICSpelled. During ground interface at heel strike, thefoot becomes a mobile adapter. This allows ac-commodation to terrain variances and posturaldeviations of the trunk, and assists in providingshock absorption. Shock absorption is a necessitysince impact stress at heel strike may exceedbody weight and may be increased to three timesbody weight during running.14Locking of the major joints of the foot trans-forms the foot into a rigid lever. This is necessaryfor normal propulsion during the late stance phaseof gait. These functions are accomplished by thejoints of the foot and ankle through the combinedactions and motions of the subtalar and midtarsaljoints during pronation and supination.G IT Y LE

The gait cycle is used as the basic reference inthe description of locomotion. This makes it pos-sible to compare walking and running very easily.One full gait cycle is the interval of time from heelstrike of one foot to heel strike by the same footat the next Therefore, there are twosteps in each gait cycle. During the gait cycle,motion occurs in both open and closed chains.Open chain motion occurs when the distal com-ponent is not,fixed and the muscle contraction isconcentric. Closed chain motion occurs when thedistal component is fixed and muscle contractionis eccentric. The gait cycle is divided into twophases, the stance phase and swing phase.Closed chain motion occurs during the stancephase and open chain motion occurs during theswing phase. The stance phase is that periodwhich begins with heel contact and ends with toe-off. The swing phase occurs between toe-off andheel strike. In normal walking, the stance phaseconsists of approximately 60 of the gait cycle,o 14,17.18and the swing phase approximately 40 OSince one complete cycle takes approximately 1sec to complete, and 60 of the cycle consistsof the stance phase, the foot is on the ground forapproximately 0.6 sec during ~a l k i ng . ~To facilitate clinical observations of the lowerextremity during locomotion, the stance phase ofgait is divided into three periods, contact, mid-stance, and propulsion.

27 of the total stance phase and is character-ized by hip joint extension and internal rotation,knee flexion, lower leg internal rotation, ankleplantarflexion, and subtalar joint and forefoot pro-nation. The lower leg and foot are viewed asfunctional units, the talus and lower leg functionas one unit, the calcaneus and foot as another.With closed chain motion, during the stance phaseof gait, the talus moves in the same direction asthe lower leg, and the foot follows the calcaneus.At heel strike, the leg is externally rotated so thesubtalar joint and forefoot are supinated. Theinitial supinated position results from the contrac-tion of the dorsiflexors and inverters of the ankleas they prepare to decelerate plantarflexion andpronation during contact. Controlled pronation oc-curs, helping with shock absorbancy. A normalfoot does not pronate beyond the contact period,and reaches its maximally pronated position atthe end of contact (Fig. 1A). The calcaneus iseverted from neutral by approximately 4-6O atthis point.l4*l8Midstance

Midstance follows contact and is characterizedby single limb support in normal walking. It con-sists of the intermediate 40 of stance phase.The primary event occurring during this period isthe conversion of the foot from a mobile adapterto a rigid lever for p r o p ~ l s i o n . ~ ~ ~ ~ ~ ~ ~ ~ ~his is ac-complished as the lower leg begins to externallyrotate, and closed chain supination occurs at thesubtalar joint. The talus abducts and dorsiflexeson the calcaneus while the calcaneus inverts.During the first part of midstance, the subtalarjoint is supinating as the rearfoot moves from amaximally pronated position back toward a neu-tral position just prior to heel lift. During the re-maining midstance period, the subtalar joint con-tinues to supinate and the rearfoot moves into asupinated position. When the neutral subtalar jointposition is reached, the midtarsal joint locks upagainst the rearfoot. rigid forefoot is producedin preparation for propulsion. This rigid state isimportant to allow for the various tendons of the

ontact leg to function around stable bony levers. Duringthis phase of gait, the trunk and lower leg moveContact begins with heel strike and ends as the forward, and the ankle is required to dorsiflex toforefoot becomes fully weight borne with the en- 10'. The knee begins to extend as the hip con-tire foot flat on the ground. Contact accounts for tinues its extension from the initial contact phase.


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6 BROWN ND Y VORSKY JOSPT Vol. 9 No. 1

Tba Fb

Talus-I CalcaneousI

Fig 1 . Normal subtalar joint motion and the neutral foot. A, At heelstrike HS) th e subtalar joint is slightly supinated. Normalpronation occurs through contact to foofflat FF). At mid stance, supination begins so that just prior to heel rise HR), the subtalarjoint is in neutral position. Supination continues through toe-off TO). The neutral foot and lower leg is illustrated in this figure incomp liance with the criteria of normalcy.

PropulsionThe final 33% of the stance phase of gait is thepropulsive portion which begins with heel lift andends with toe-off. The body weight is shifted fromthe lateral side of the foot to the medial side andto the great toe. This is accomplished by contin-ued closed chain supination at the subtalar jointas the leg continues to externally rotate. Thisincreases the skeletal efficiency of the foot as itcontinues to function as a rigid lever. The anklemoves from its terminally dorsiflexed position of

10to its terminally plantarflexed position of 20The knee rapidly flexes and the hip continues toexternally rotate and flex. The final phase of pro-pulsion requires the first metatarsophalangealjoint to be stabilized, enabling it to dorsiflex ap-proximately 70as the weight is being transferredfrom the first ray to the great toe, and finally tothe opposite foot.CHANGES WHICH OCCUR IN RUNNINGGAIT

Running gait differs from normal ambulation inthat there is an airborne float phase when neitherfoot is in contact with the ground. This producestwo primary changes in the running gait: an in-creased magnitude of the vertical ground reactionforces and a progressive shortening of the stancephase of gait.794.17318321

As the speed of gait increases, the verticalground reaction forces increase from 70-80% ofbody weight during walking to approximately275-300% during running.14 This occurs as a

result of Newton's third law: for every action thereis an equal and opposite reaction. Other groundreaction forces such as fore and aft shear, medialand lateral shear, and torque demonstrate essen-tially the same patterns for walking and runninggait, but the magnitudes of these forces increasesomewhat with r~nn ing .~ , '~As the speed of gait increases, there is a pro-gressive decrease of total stance time from 0.6sec during walking to 0.2 sec during running.Therefore, all events which normally occur duringstance must occur approximately three timesfaster in running than in walking. This markeddecrease in stance phase and the marked in-crease in ground reaction forces are the primaryreasons given for injuries to runners.21CRITERIA FOR NORMALCY

A normal lower leg and foot is one which, duringlocomotion, places no undue stress upon itself orthe proximal joint^.^ The criteria for normalcy,described below, represent the ideal physical re-lationship of osseous segments of the foot andleg which should be present for maximum effi-ciency during loc~motion.'~eldom seen clini-cally, these relationships represent a basis forevaluation of the degree of deformity present.Once the criteria for normalcy are evaluated, anydeviation from one criterion constitutes deformityor abnormality.'The criteria for normalcy are as follows: thedistal one-third of the lower leg is vertical or in thesagittal plane; the subtalar, ankle, and knee jointslie in the transverse plane parallel to the ground;


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JOSPT July 987 LOCOMOTOR BIOMECHANICS AND PATHOMECHANICS 7the subtalar joint is in its neutral position, neitherpronated nor supinated; bisection of the posteriorsurface of the calcaneus is vertical or inverted nomore than 3-4 from the vertical; the midtarsaljoint is locked in its maximum position of prona-tion; the metatarsals and plantar surface of thecalcaneus lie parallel to each other in the trans-verse plane; and last, there are no rotational ortorsional influences present in the lower leg. Fig-ure 1B illustrates this ideal physical relationship.During locomotion, all normal criteria should bepresent just prior to heel lift. Deviations fromnormalcy in the biomechanical system may causeabnormal motion and stress to occur during thestance phase of gait. This may, in turn, be mani-fested in the form of a stress injury.'P THOMECH NICS

As defined previously, locomotor biomechanicsis the application of mechanical laws to livingsystems in motion. Pathomechanics can then bedefined as the mechanics of living systems inmotion resulting in, or leading to, dysfunction orinjury. The remainder of this article is devoted tothe pathomechanics of the ankle and foot includ-ing common intrinsic abnormalities, resultantpathological states, and treatment options.In order to understand the pathomechanics ofthe ankle and foot, one must first understand theconcept of compensation. Compensation is de-fined by Root et al.'' as a change of structure,position, or function of one part of the body in anattempt to adjust to a deviation of structure,position, or function of another body part. Morebasically stated, compensation is the counterbal-ancing of any defect in structure or f~nction.~There are two types of compensation, normal andabnormal. Normal compensation maintains bal-ance and produces no abnormality or pathology.An example of normal compensation is the ad-aptation of the foot to variations in surface terrain.Abnormal compensation is an adjustment for ab-normal structure or function of the body which,upon repetitive demand, may lead to pathology.In the foot, both types of compensation, normaland abnormal, result from pronation and supina-tion of the subtalar and midtarsal joints. Whenbony or soft tissue deformities of the foot or lowerextremities are present, abnormal compensatorypronation or supination may result. Each is dis-cussed below.Pronation is considered abnormal when it is inexcess of the amount required, or when it occurs

when supination should be occurring during lo-comotion.18 Normal minimum pronation requiredduring walking locomotion has been shown to be6 , with maximum values averaging 9.4 and astandard deviation of 3.53,'8,21Excessive pro-nation can then be defined as 13 or greater.According to S~botnick,~'he most commoncause of foot pathology is abnormal compensa-tory pronation because the foot is abnormallyunstable in a weightbearing situation. This leadsto hypermobility, subluxation, resultant micro-trauma, and Causes of abnormalcompensatory pronation can be intrinsic or extrin-sic to the foot. This paper focuses only on theintrinsic causes. They include subtalar varus, fore-foot varus, forefoot supinatus, forefoot valgus,and ankle joint equinus.Abnormal supination is excessive supination, orsupination that occurs when pronation should beoccurring during normal gait. Normal values forsupination have been shown to range from 612'8,21 Compensation for a forefoot valgus,plantarflexed first ray, or equinus deformity cancause abnormal supination. Pathology may alsooccur when motion is restricted or when it isinsufficient for normal locomotion. Disease,trauma, contracture, or congenital coalition maybe some causes of these problems. The followingare descriptions of common intrinsic abnormalitiesof the foot.Subtalar Varus

Subtalar varus, as illustrated in Figure 2A, is aninversion deformity of the calcaneus due to anincomplete derotation of the posterior calcaneusfrom its'infantile position.'' In childhood, the cal-caneus derotates 3-4 . If this derotation is incom-plete or does not occur, subtalar varus re-s u l t ~ . ~ . ~ ~ ' 'ompensation or this deformity duringlocomotion requires calcaneal eversion to verticalat heel strike in order for the condyles of thecalcaneus to reach the ground. The foot remainspartially pronated at heel lift not allowing the sub-talar joint to supinate to neutral n early propulsion.The first ray is not adequately stabilized by theperoneus longus muscle and hypermobility ispresent. Increased oad and shear forces are pres-ent beneath the second metatarsal headT8.Oncethe heel is off the ground, the normal forefootsupinates in an attempt to become a rigid lever.Abnormal compensatory pronation occurs onlyduring the time the abnormal calcaneus is inground contact (Fig. 28).


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Fig 2. Subtalar varus. A, Subtalar varus deformity is illustrated as seen when in the subtalar joint neutral position. It is an inversionosseous deformity of the calcaneus in the neutral position. 8 bnormal compensatory pronation begins at heel-strike HS) andcontinues until heelrise HR ) when the abnorm al calcaneus is no longer in contact with the ground. The foot supinates late afterheelrise HR) in time for propulsion to be fairly normal. Abnormal cycle shown in broken line.)

Abnormal compensatory pronation for a sub-talar varus may result in pathology. Plantar kera-toses beneath the second metatarsal head maydevelop due to increased shear, inflammation, andhyperplasia. Soft tissue lesions may also developsuch as peroneus longus tendinitis due to insuffi-cient first ray stabilization, posterior tibialis tendi-nitis due to excessive deceleration of pronation,or Achilles tendinitis due to excessive active su-pination. Articular lesions may develop at the pa-tellofemoral joint due to the antagonistic state ofmaximum pronation and maximum knee flexionnot occurring sim~ ltaneous ly .'~'~~~~

orefoot VarusForefoot varus, as illustrated in Figure 3A, is afixed congenital osseous deformity of the forefootin which the plane of the lesser metatarsals isinverted in relation to the calcaneus in subtalarjoint neutral position. Forefoot varus is caused bya failure of the head and neck of the talus to fullyderotate from the infantile po~ition.~.'~t is themost common cause of abnormal compensatory

pr~nat ion.~~The pathomechanics of compensated forefootvarus are much more destructive than subtalarvarus. Once the condyles of the calcaneus are onthe ground, the subtalar joint must continue topronate in order for the first ray to reach theground. The calcaneus then everts past the neu-tral position and at heel rise, the foot is in maxi-mum pronation. The forefoot remains in pronationthroughout propulsion resulting in severe instabil-

ity. The first ray is hypermobile and the secondmetatarsal takes most of the force during propul-sion.Figure 3B illustrates how abnormal compensa-tory pronation occurs throughout stance and pro-pulsion in a compensated forefoot varus. Thisresults in more destructive pathologies in the softtissues and bony tissues mentioned previouslywith subtalar varus. The pronated position of theforefoot during propulsion can also lead to fore-foot pathology.Predisposing factors to the development offorefoot pathology are the amount of first rayhypermobility and the congenital angulation of thelongitudinal axis of the metatarsals to the rear-foot. Hypermobility of the first ray during pro-pulsion results from the inability of the peroneuslongus to stabilize sufficiently. Hypermobility canlead to subluxation of the first metatarsophalan-geal joint.Subluxation in the transverse plane can resultin hallux-abductovalgus (HAV) deformity,8918ub-luxation in the sagittal plane can result in halluxlimitus deformity. The determining factor in thedevelopment of HAV or hallux limitus is the con-genital angulation of the forefoot to rearfoot. Themore adducted the forefoot, the more likely a HAVis to develop. Conversely, a more rectus forefootwould more likely lead to a hallux limitus.18Forefoot supinatus is a reducible, acquired softtissue contracture at the midtarsal joint resultingin supination of the forefoot.' Supination contrac-ture may occur about either the oblique or longi-


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JOSPT July 987 LOCOMOTOR BIOMECH NICS ND P THOMECH NICS

Fig 3. Forefoot varus. A, Forefoot varus is an osseous deformity of the talus in which the forefoot is inverted relative to thecalcaneus in subtalar joint neutral position. 6 n order to get th e inverted forefoot to the ground, abnormal compensatory pronationoccurs. Pronation is excessive and continues from foofflat FF) throughout the stance phase of gait into propulsion. Abnormalcycle shown in broken line.)tudinal axis of the midtarsal joint. Forefoot supi-natus about the oblique axis results in forefootadduction, plantarflexion, and slight inversion.Clawing of the toes may result from the transverseplane instability caused by the relatively abductedposition of the phalanges to the metatarsals inoblique axis forefoot supinatus. Supinatus aboutthe longitudinal axis is difficult to differentiate romforefoot varus. However, it is attributed to con-tracture or spasm of the anterior tibialis muscleresulting n dorsiflexion of the first ray and forefootsupination rather than talar pathology seen inforefoot varus. Abnormal compensatory pronationis the result of either forefoot supinatus and re-sultant pathologies including those previouslymentioned for subtalar and forefoot varus.18Forefoot Valgus

Forefoot valgus, as illustrated in Figure 4A, isan osseous deformity of the forefoot in which theplane of the lesser metatarsals is everted relativeto the calcaneus in subtalar oint neutralposition18Heel strike is normal with forefoot valgus, but theforefoot is prematurely loaded. The first ray isstable, and abnormal compensatory supinationoccurs at the subtalar joint resulting in absenceof normal pronation during midstance and latepronation at heel-off to allow knee f l e ~ io n . ~ , ~Forefoot valgus can take the form of a plantar-flexed first ray or a total forefoot valgus. Figure4 8 illustrates the absence of normal pronationduring stance with forefoot valgus as well as lateabnormal compensatory pronation.

Abnormal supination occurring during mid-stance can lead to pathologies related to lack ofshock absorption in the upper leg, but also todevelopment of plantar lesions beneath the fifthand first metatarsals. Abnormal pronation occur-ring late in propulsion can lead to hallux subluxa-tions previously discussed for forefoot v a r ~ s . ~ ~ ~Equinus

Ankle equinus is a fixed limitation of dorsiflexionat the ankle joint to less than 10 when in thesubtalar neutral position and with the knee ex-tended. Compensation takes place at the sub-talar and midtarsal joints in the form of abnormalpronation allowing dorsiflexion of the forefoot onthe rearfoot. Abnormal pronation is present duringpropulsion resulting in hypermobility of the firstray. Resultant pathologies are those noted previ-ously for abnormal pronation occurring throughpropulsion including keratoses and hallux deform-ities, but symptoms seem to occur earlier in lifeand are resistant to conservative manage-ment.10,22923CONCLUSION

Ankle and foot biomechanical abnormalitiesmay occur independently or in combination. Anunderstanding of normal and abnormal locomotorbiomechanics is essential for effective patientcare. Once normal mechanics are understood,pathomechanics can be identified and the etiologyof patient complaints postulated. It is necessary


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Fig 4 . Forefoot valgus. A, F orefoot valgus is an osseous deformity of the forefoot in which the forefoot is everted relative to thecalcaneus in subtalar joint neutral position. 6 Abnormal supination occurs as the forefoot is prematurely loaded after heelstrikeHS ). Pronation is insufficient, then occurs late in stance at heel-off HO ) to allow knee flexion. Abnormal cycle shown in brokenline.)to treat not only the symptoms but also the cause 8. Hlavac H: compensated forefoot varus. J Am Podiatry Assocof the dysfunction. 60:229-233.19709. lnrnanVT: The human foot. Manitoba Med Rev 46:513-515,1966A comprehensive treatment regimen must in- l o Inmanvr MannRA: Biomechanics of the foot and ankle. In: Mannclude a thorough biomechanical evaluation ap- RA (ed), DeVries Surgery of the Foot, c h 1, pp 3-21. s t Louis:cvMosby Co, 1978propriate for pain and 11. Inman Ralston HJ, Todd F: Human Walking. Baltimore: Wil-therapeutic exercise to restore normal length/ liams 8 Wilkins, 1981strength/function of musculature and exercises 12. Isman RE, lnrnan VT: Anthropometric studies of the human footand ankle. Bull Prosthet Res 97:76, 1969enhance P ~ ~ P ~ ~ ~ ~ ~r- 13. Kapandji JA: The Physiology of the Joints, Val 2 New Yo*:thotic devices to correct biomechanical abnor- churchill-~ivingstone, 970malities may be indicated to help decrease ab- 14. Mann RA: Biomechanics of running. In: Mock RP (ed), Symposiumnormal compensation. Early identification of on the Foot and Leg in Running Sports, pp 1-29, St Louis: CVMosby Co, 1982biomechanical dysfunction and proper interven- 15. ManterJT: Movements of the subtalar and transverse arsal oints.Anat Rec 80:397,1941for and decreased 16. Mumy MP, Drought AB. Kory RC: Walking patterns of nonnallikelihood for recurrence of injury in the future. men. J Bone Joint Surg (Am) 46:335-344,196417. Root ML, Orien WP, Weed JH: Biomechanical Examination of theREFEREN ES Foot. LOS Angeles: Clinical Biomechanics Corporation, 197118. Root ML, Orien WP, Weed JH: Normal and Abnormal Function of1. Bates BT, Ostemig LR, Mason JR, James SL: Functionalvariability the Foot. Los Angeles: Clinical Biomechanics Corporation, 1971of the lower extremity during the support phase of running. Med 19. Sammarco GJ, Burstein AH, Frankel VH: Biomechanics of theSci Sports Exerc 11:328-331,1979 ankle: a kinematic study. Orthop Clin North Am 4:75-83, 19732. Calliet R: Foot and Ankle Pain. Philadelphia: FA Davis Co, 1968 20. Smidt GL: Biomechanics and physical therapy: a Perspective. Phys3. ClarkeTE, Frederick EC, Hamill C: The study of rearfoot movement Ther 64:1807-1808,1984in running, In: Frederick EC ( ), Sports Shoes and Playing Sur- 21. Subotnick SI: Biomechanics of the subtalar and midtarsal oints. Jfaces, Ch 10, pp 116-189. Champaign, IL: Human Kinetics Pub Am Podiatry Assoc 65:756-764, 1975

lishers Inc. 1984 22. Subotnick SI: The biomechanics of running: implications for the4. Close JR, lnrnan VT Poor PM, Todd BA: The function of the prevention of foot injuries. Sports Med 2:144-153, 1985subtalar joint. Clin Orthop 50:159-179. 1967 23. Subotnick, SI: The flat foot. Phys Sports Med 9:85-91, 19815. Dorland's Illustrated Medical Dictionary, ED 25, p 345. Philadelphia: 24. Taber CW: Taber's Cyclopedic Medical Dictionary, Ed 14, pp 179.WB Saunders Co, 1974 Philadelphia: FA Davis Co, 19776. Ebisui JM: The first ray axis and the joint. J Am Podiatry Assoc58:160-168,19687. Gray G: When The Feet Hit the Ground, Everything Changes.Toledo: American Physical RehabilitationNetwork, 1984

Locomotor Biomechanics and Pathomecanics a Review

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