Surfaces.The anterior surface is convex from side to side, and subdivided by two ridges into three facets, for articulation with the three cuneiform bones. The posterior surface is oval, concave, broader laterally than medially, and articulates with the rounded head of the talus. The dorsal surface is convex from side to side, and rough for the attachment of ligaments. The plantar surface is irregular, and also rough for the attachment of ligaments. The medial surface presents a rounded tuberosity, the lower part of which gives attachment to part of the tendon of the Tibialis posterior. The lateral surface is rough and irregular for the attachment of ligaments, and occasionally presents a small facet for articulation with the cuboid bone.
Articulations.The navicular articulates with four bones: the talus and the three cuneiforms; occasionally with a fifth, the cuboid.
The First Cuneiform Bone (os cuneiform primum; internalcuneiform) (Figs. 278,279).The first cuneiform bone is the largest of the three cuneiforms. It is situated at the medial side of the foot, between the navicular behind and the base of the first metatarsal in front.
Surfaces.The medial surface is subcutaneous, broad, and quadrilateral; at its anterior plantar angle is a smooth oval impression, into which part of the tendon of the Tibialis anterior is inserted; in the rest of its extent it is rough for the attachment of ligaments. The lateral surface is concave, presenting, along its superior and posterior borders a narrow L-shaped surface, the vertical limb and posterior part of the horizontal limb of which articulate with the second cuneiform, while the anterior part of the horizontal limb articulates with the second metatarsal