The hindfoot refers to the most posterior section of the foot, where the talus, or ankle bone, and calcaneus, or heel bone, are situated. It may also refer to the joints contained therein, which include the subtalar and talocrural joints. Hindfoot may also include the muscles that attach along these bones, their tendons, and the ligaments holding these bones together.
More tendons and ligaments and larger bones are found in the hindfoot than in the forefoot, which includes the phalangeal bones of the toes and metatarsal bones just ahead of the arch, or the midfoot, which includes the five tarsal bones of the arch of the foot. The hindfoot has the fewest bones, however, consisting only of the remaining two bones of the tarsus: the talus and calcaneus. Two major synovial joints are found here as well. The talocrural or ankle joint is situated between the superior surface of the talus and the base of the tibia and fibula in the lower leg, and the subtalar joint is located between the inferior surface of the talus and the superior surface of the calcaneus.
Known as a hinge joint, the talocrural is a joint that moves the foot front to back in two motions known as dorsiflexion and plantarflexion, respectively. Most of the surface of this joint lies between the talus and the larger tibia bone, but a portion also lies between the broad talus and the narrower fibula. On the underside of the talus where it meets the calcaneus is the subtalar joint, also a synovial hinge joint but with movement occurring perpendicular to that of the talocrural. The subtalar is the articulation in the hindfoot that permits inversion and eversion, or the rolling of the foot from side to side so that the sole faces inward and outward, respectively.
Several tendons of extrinsic muscles found in the lower leg penetrate the hindfoot and cause these four movements, many of which attach to the two bones located here. Dorsiflexion, or the upward flexing of the foot, is initiated by several muscles of the shin, among them the tibialis anterior, extensor digitorum longus, and extensor hallucis longus, all of which have tendons crossing the hindfoot. Plantarflexion, or the downward pointing of the foot, is the responsibility of the gastrocnemius, soleus, and plantaris muscles in the calf. The tendons of all three converge to form the Achilles tendon, which attaches to the heel bone.
Inversion of the ankle is caused by muscles on the medial or inner side of the calf, including the tibialis posterior and tibialis anterior, both of whose tendons cross the subtalar joint. Eversion of the ankle is the result of contractions of the three peroneal muscles on the lateral or outer side of the calf, the peroneus longus, brevis, and tertius. Likewise, each features a tendon that crosses the hindfoot and pulls sideways on the subtalar joint.