[Anatomy and kinematics of the human ankle joint].

In the ankle (talocrural) joint, the lower end of the tibia and fibula embrace the trochlea tali. Thus, an approximately uniaxial joint is formed which permits dorsiflexion and plantarflexion of the foot against the leg. Due to the geometry of the trochlea tali, conjunct lateral rotation of the fibula against the tibia occurs at the tibiofibular articulations synchronously with active dorsiflexion at the ankle joint. Movements at the talocrural joints are mainly limited by the opposing muscles as well as by strong collateral ligaments. Talus and calcaneus form a functional unit connected by posterior and anterior articulations. The posterior articulation is the subtalar (talocalcaneal) joint; in the anterior articulation, talar facets of the calcaneus together with the posterior surface of the navicular and the superior fibrocartilaginous surface of the plantar calcaneonavicular ligament form a concavity for the talar head. Thus, the talocalcaneonavicular joint is a compound and--like the subtalar joint--a multiaxial articulation. On the weight-bearing foot, the distal tarsus and metatarsus are pronated and supinated against the talus in order to maintain plantigrade contact. When the foot is off the ground, these movements are modified to eversion and inversion, also involving the calcaneocuboid joint. In addition, movements between the calcaneus and cuboid also occur during pronative or supinative changes between the fore- and hindfoot. Limitation of movements is due to leg muscles as well as strong ligaments. Finally, the cuneonavicular, cuboideonavicular, intercuneiform and cuneocuboid joints permit some additional alterations of the loaded foot in contact with the ground.