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The demands placed on the foot and toes require a delicate balance between the need to provide a rigid platform and the ability to remold itself to adapt to uneven terrain. The foot acts as a rigid lever during the preswing phase of gait and as a shock absorber during the initial contact and loading response phases (Fig. 8-1). When running, the foot is required to absorb and dissipate approximately three times a person’s body weight.1
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The foot relies on close and precise relationships with the various surrounding structures. True one-to-one articulation between the bones within the foot is rare, tending to be limited to the joints of the toes. The majority of bones have multiple articulations with their contiguous structures. The muscles originating off the bones of the foot (intrinsic muscles) and the extrinsic muscles originating from the lower leg provide motion and support.
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Formed by 26 structural bones, the foot has three regions: the rearfoot (or hindfoot), the midfoot, and the forefoot (Fig. 8-2). The tarsals consist of the calcaneus, talus, navicular, cuboid, and three cuneiforms. Articulating with the distal tarsals, each of the five metatarsals (MTs) leads to the proximal phalanges. Each toe consists of three phalanges (proximal, middle, and distal), with the exception of the great toe, which has only two phalanges (proximal and distal). Two sesamoid bones are found in the flexor hallucis brevis tendon beneath the first metatarsophalangeal (MTP) joint. The bony landmarks of the foot are presented in Figure 8-3.
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The rearfoot, formed by the calcaneus and talus, provides stability and shock absorption during the early stance phase of gait and serves as a lever arm for the Achilles tendon during plantarflexion. The calcaneus is the largest of the tarsal bones. Its most prominent feature is the posteriorly projecting calcaneal tubercle. The large size of this tubercle provides a mechanically powerful lever for increasing the muscular force produced by the triceps surae muscle group (the gastrocnemius and soleus), which inserts on the ...