C lin ic a l P e r spe c t iv e F o o t a n d A n k l e B iomechanics ABSTRACT: Foot and ankle injuries are common in sportsmen and the general population. The impact that the functional anatomy and bio­ HUNTER L J, BSc PHYSIOTHERAPY mechanics of the foot and ankle complex has on normal gait is reviewed. FORTUNE J, BSc PHYSIOTHERAPY2 The abnormal biomechanics associated with overpronation and over­ Physiotherapy Department, University of the Witwatersrand supination are discussed, as are their consequences. The management Physiotherapy Department University of the Witwatersrand principles of foot and ankle injuries are briefly described. KEYWORDS: FOOT AND ANKLE BIOMECHANICS, OVERPRONATION AND OVERSUPINATION INTRODUCTION FIGURE 1. The joints of the ankle and foot contribute to the combination of Foot and ankle injuries are extremely movements that occur during gait. (Adapted from "Reid D 1992 Sports injury common, both in sportsmen and in assessment and rehabilitation. New York: Churchill Livingstone.) the general population (Rundle, 1995). Fifty-three percent of all basketball injuries, and 31% of soccer injuries involve the foot and ankle (Garrick, 1977). Ankle sprains account for the most time lost by athletes due to injury (Reid, 1992). The estimated incidence of ankle sprains is 1:10 000 people per day in the United States (McCulloch, et al, 1985). ) . The predisposition to injury of the 3 1 foot and ankle complex can only be 0 2 understood by studying the anatomy and d e biomechanics of this region. t a d ( THE ANATOMY (See Figure 1.) r e h s i l 1. Talocrural Joint b u The ankle is a uniaxial hinge joint. The P medial and lateral malleoli (mortice) and e h t the talus, also known as the talocrural y joint, have an inherent bony stability. b d The position and orientation of the e t ligaments (predominantly the lateral li­ n a gament complex, the deltoid or medial r g ligament and ligaments of the syndes­ e c n mosis) further enhance this passive sta­ M idfoot ___________I I____________ Forefoot ____________ I e c bility. The muscles crossing the ankle i l r (flexor hallucis brevis; flexor digitorum; e d gastrocnemius; soleus; peroneus longus; complex, and Boruta et al (1990), n u brevis and tertius; extensor digitorum include the lateral talocalcaneal liga­ CORRESPONDENCE: y longus and extensor digitorum brevis) ment as a fourth component of the com­ a L J Hunter w provide active stability. plex, but most authors are in agreement Physiotherapy Department e t a Figure 2.1 show the lateral ligament about the ligaments named above. University of the Witwatersrand G complex consisting of the anterior talo­ The ATL is long and thin and may be t 7 York Road e n fibular ligament (ATL), the calcaneo- considered a thickening of the anterior Parktown i b fibular ligament (CFL) and the posterior joint capsule. Because of its orienta­ 2193 a S talofibular ligament (PTL). Renstrom tion, its main function is to limit inver­ Tel: (O il) 488-3450/2 (w) y b and Konradsen (1997) include the sub­ sion while the foot is plantar flexed (011)465-4615 (h) d e talar ligaments in the lateral ligament (Rasmussen, 1985). The ATL is relaxed Fax: (011)488-3210 c u d o SA Jo u r n a l o f Physiotherapy 2000 V o l 56 No 1 17 r p e R FIGURE 2.1. The lateral ligament complex consisting of the anterior talofibular Figure 2.2 shows the medial or deltoid ligament, the calcaneofibular ligament and the posterior talofibular ligament. ligament. The deltoid ligament is strong (Adapted from "Reid D 1992 Sports injury assessment and rehabilitation. and therefore much less likely to be New York: Churchill Livingstone.) injured. It limits eversion of the ankle. If the deltoid ligament is damaged, an associated fracture of the lateral mal­ leolus or a tearing of the tibiofibular 1 syndesmosis must be excluded. The hinge joint allows dorsi and plan­ tar flexion with some accessory gliding. Dorsi and plantar flexion movement does not occur in one plane, but three (the triplanar movement of the ankle). This is due to the asymmetrical shape of the body of the talus, and the obliquity of the ankle joint axis (approximately 40° anterior of the frontal plane on the medial side of the ankle) (Norkin and Levangie, 1992). The ‘components’ of dorsi and plantar flexion will vary, depending on whether the movement is performed in an open chain or a closed chain. In an open chain movement, i.e. the foot is free and non­ FIGURE 2.2. The medial or deltoid ligament complex consisting of the posteri­ weight bearing, dorsi-flexion involves or tibiotalar fibres, tibiocalcaneal fibres, and tibio-navicular fibres. The plantar abduction and eversion, and plantar calcaneo-navicular ligament is depicted. (Adapted from "Reid D 1992 Sports flexion includes adduction and inver­ ) . injury assessment and rehabilitation. New York: Churchill Livingstone.) sion. However, during a closed chain 3 1 movement, i.e. weight bearing position, 0 2 dorsiflexion includes adduction and d e inversion, and plantar flexion involves t a abduction and eversion. Patients with d ( foot and ankle problems must therefore r e be assessed in weight-bearing and non­ h s i l weight bearing positions e.g. lying and b u standing (Donatelli, 1996). P The most stable position of the ankle e h t is in dorsiflexion as the talus ‘locks’ y into the ankle mortice (the close-pack b d position). Conversely plantar flexion is e t the most unstable position. n a r g 2. Subtalar Joint e c n This is the articulation between the cal­ e c caneus and the talus, i.e. the rearfoot. i l r Supination and pronation occur at the e d subtalar joint, in combination with n u accessory movements. Abduction and y a in the neutral position of the foot. The 1997), but it may be taut in dorsiflexion dorsiflexion occur with pronation, and w e CFL is relaxed in normal standing and (Renstrom and Konradsen, 1997) or in adduction and plantar flexion with t a does not have a major role in talotibial eversion and plantar flexion (Rundle, supination. This movement of the sub­ G t joint stability. It appears to limit exces­ 1995). Donatelli (1996) claims the PTL talar joint alters the rearfoot and forefoot e n sive dorsiflexion and acts as a guide is the prime stabiliser during plantar angles (Heil, 1992), and allows the foot i b for the axis of subtalar joint motion flexion. The lateral ligament complex to adapt to changes in terrain. When a S (Renstrom et al, 1988). The role of the is therefore vulnerable to injury during the subtalar joint is in a neutral position, y b PTL is unclear and controversial dorsiflexion, plantar flexion and inver­ the joints of the foot, ligaments and ten­ d e (Rundle 1995, Renstrom and Konradsen, sion. dons of the foot are least stressed. c u d o 18 SA Jo u r n a l o f Physiotherapy 2000 V o l 56 No 1 r p e R This is the position in which the foot terminal swing and pre-swing. The may well result in dysfunction of, and best supports the body’s weight (Heil, swing phase is divided into initial swing, pain in, the other joints of the lower limb 1992). mid swing and terminal swing (Norkin and spine, especially the knee, midtarsal and Levangie, 1992; Donatelli, 1996). and forefoot joints. 3. Midtorsal Joint At initial contact, (See Table 1) the This joint complex consists of the cal­ heel strikes the ground on its lateral ABNORMAL BIOMECHANICS caneocuboid and talonavicular joints, aspect. The body’s weight is transmitted Abnormal pronation and supination which link the subtalar joint with the down through the tibia and talus, which result in hypermobility and hypomobility forefoot. Due to the shape of the arti­ is medial to the ground reaction force. of the foot respectively (Donatelli, cular surfaces, the movements in the This results in adduction of the talus, 1996). midtarsal joint occur in combination, i.e. which initiates and produces pronation The overpronated foot can be recog­ plantar flexion and adduction occur with of the foot. The pronation ‘unlocks’ the nised by an everted calcaneus, medial supination, and dorsiflexion and ab­ midtarsal joint, allowing the foot to bulging of the navicular tubercle, abduc­ duction occur with pronation (Donatelli, absorb shock and adjust to the terrain. tion of the forefoot relative to the rear- 1996). Supination occurs during early mid- foot and a reduced height of the medial stance, bringing the foot to a neutral longitudinal arch (Donatelli, 1996). NORMAL BIOMECHANICS position at midstance. Supination conti­ This should be assessed in standing. The normal biomechanics of the foot nues during the midstance and toe-off Abnormal pronation results in a and ankle depend on static and dynamic (pre-swing) stages. This is essential as reduced time for resupination of the foot components. The bones, articular sur­ supination ‘locks’ the midtarsal joint to occur (Paulsen, 1991). The forefoot face congruity, ligaments and fascia con­ making the foot into the rigid lever nec­ remains unlocked and hypermobile, stitute the static component. The dyna­ essary for effective push-off. which reduces its ability to bear weight, mic component depends on muscle work During the swing-through phase the and substantially reduces its effective­ and movement of the tarsal bones. The foot moves from plantar flexion to ness as a rigid lever for push-off. If this is functions of the foot and ankle are to dorsiflexion and is relaxed.