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This bone is situate at the forepart of the astragalus and inner part of the foot. The posterior surface forms a cavity, somewhat like that of a boat, for receiving the head of the astragalus. There is a prominence at the inner side of the bone, for the insertion of tendons, muscles, and strong ligaments. The forepart of the bone is convex, and divided into three articular surfaces for articulation with the ossa cuneiformia. Between the os naviculare and astragalus, the foot has its principal lateral and rotary motions; although each of the other joints of the tarsus contributes a little. Part of the tibialis posticus is inserted into it.