The Cuboid is the lateral bone of the distal row of the tarsus, situated in front of the calcaneum and behind the fourth and fifth metatarsal bones. It has six surfaces.
- The proximal surface is concavoconvex and articular.
- The plantar surface is marked anteriorly by an oblique groove.
- The lateral surface is much shorter than the medial, and is notched.
- The proximal surface is concavoconvex for articulation with the calcaneum.
- The distal surface is also articular. It is divided by a vertical ridge into two areas for the fourth and fifth metatarsal bones.
- The dorsal surface is rough for the attachment of ligaments. It is directed upwards and laterally.
- The plantar surface is crossed anteriorly by an oblique groove. The groove is bounded posteriorly by a prominent ridge.
- The lateral surface is short and notched.
- The medial surface is extensive, being partly articular and partly non-articular. An oval facet in the middle articulates with the lateral cuneiform bone. Proximal to this a small facet may present for the navicular bone.
- The notch on the lateral surface, and the groove on the plantar surface, are occupied by the tendon of the peroneus longus.
- The ridge posterior to the groove gives attachment to the deep fibres of the long plantar ligament.
- The short plantar ligament is attached to the posterior border of the plantar surface.
- The posteromedial part of the plantar surface provides (a) insertion to a slip from the tibialis posterior; and (b) origin to the flexor hallucis brevis.
- The nonarticular part of the medial surface provides attachment to ligaments, including the lateral limb of the bifurcate ligament.
The cuboid bone ossifies from one centre which appears just before birth.