talus fracture is accompanied by a dislocation, restoration of articular and axial alignment is necessary to optimize ankle and hindfoot function. As dice Dice were originally made from the talus of hoofed animals, leading to the nickname "bones" for dice. Colloquially known as "knucklebones", these are approximately tetrahedral. Modern Mongolians still use such bones as shagai for games and fortune-telling, with each piece relating to a symbolic meaning. In other animals The talus apparently derives from the fusion of three separate bones in the feet of primitive amphibians; the tibiale, articulating with tibia, the intermedium, between the bases of the tibia and fibula, and the fourth centrale, lying in the mid-part of the tarsus. These bones are still partially separate in modern amphibians, which therefore do not have a true talus. The talus forms a considerably more flexible joint in mammals than it does in reptiles. This reaches its greatest extent in artiodactyls, where the distal surface of the bone has a smooth keel to allow greater freedom of movement of the foot, and thus increase running speed. In non-mammal amniotes, the talus is generally referred to as the astragalus. In modern crocodiles the astragalus bears a peg which inserts into a corresponding socket on the calcaneum, and the hinge of the ankle joint runs between the two tarsals; this condition is referred to as "croc-normal"; this "croc-normal" condition was likely ancestral for archosaurs. In dinosaurs (including modern birds) and pterosaurs, the hinge of the ankle instead is distal to the two tarsals. Far rarer are archosaurs with a "croc-reversed" ankle joint, in which the calcaneus bears a peg whilst the astragalus bears a socket. In the theropod dinosaur lineage leading to birds, the astragalus gradually increases in size until it forms the entire proximal facet of the ankle articulation; additionally the anterior ascending process gradually extends increasingly proximally. In modern birds the astragalus is fused with the tibia to form the tibiotarsus. Additional images See also Squatting facets Knucklebones, a dice game using astragali Shagai Notes References External links Anatomy of the talus by Maurice Laude, Laboratory of Anatomy and Organogenesis, Amiens Medical School Fractures of the Talus at mdmercy.com () Illustration at orthoinfo.aaos.org Skeletal system Bones of the lower limb Bones of the foot Tarsal bones