Anatomy and arthrokinematics of the human ankle and intertarsal joints

In the ankle (talocrural) joint, the lower end of the tibia and fibula embr ace the trochlea tali. Thus,an approximately uniaxial joint is formed which permits dorsiflexion and plantarflexion of the foot against the leg. Due t o the geometry of the trochlea tall, conjunct lateral rotation of the fibul a against the tibia occurs at the tibiofibular articulations synchronously with active dorsiflexion at the ankle joint. Movements at the talocrural jo ints are mainly limited by the opposing muscles as well as by strong collat eral ligaments. Talus and calcaneus form a functional unit connected by pos terior and anterior articulations. The posterior articulation is the subtal ar (talocalcaneal) joint; in the anterior articulation, talar facets of the calcaneus together with the posterior surface of the navicular and the sup erior 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 weightbearing 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 in version, also involving the calcaneocuboid joint. In addition, movements be tween the calcaneus and cuboid also occur during pronative or supinative ch anges between the fore- and hindfoot. Limitation of movements is due to leg muscles as well as strong ligaments. Finally, the cuneonavicular, cuboideo navicular, intercuneiform and cuneocuboid joints permit some additional alt erations of the loaded foot in contact with the ground.