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Other Terms: Articulatio talocalcaneonavicularis, Articulation talocalcanéonaviculaire
The talocalcaneonavicular articulation is the joint formed by the head of the talus, the anterior and middle articular facets of the calcaneus, the posterior articular facet of the navicular, and the navicular fibrocartilage of the plantar calcaneonavicular ligament. The joint is a complex, compound articulation, and includes an anterior talocalcaneal and a talonavicular articulation. The socket for the head of the talus is formed by four different cartilage-covered surfaces. The articulation is separated from the posterior calcaneotalar joint by the sinus of the tarsus and its articular capsule exhibits no special peculiarities. From a functional standpoint the talocalcaneo-navicular joint is composed of two portions. The first of these is the joint between the talus and the navicular bone, which acts together with the calcaneocuboid articulation. It is an ellipsoidal joint, while the talonavicular articulation is a saddle-joint. Although these joints are biaxial, they check each other reciprocally, so that during motion each joint loses one of its axes of movement and a common uniaxial hinge joint results, the transverse tarsal joint. The remaining portion of the talocalcaneonavicular joint acts together with the talocalcaneal joint, whose axis coincides with that of the transverse tarsal joint. Both joints, or rather both combinations of joints, always work together. During inversion there is also an elevation of the inner margin of the sole of the foot (supination), and during eversion there is a simultaneous elevation of the outer margin of the sole of the foot (pronation).