The Carpus consists of eight bones arranged in two rows of four. The proximal row beginning from the radial side are scaphoid, semilunar, cuneiform, and pisiform; the distal row, beginning from the radial side, are trapezium, trapezoid, os magnum and unciform. They are all small irregular-shaped bones articulating with one another. The bones are articulated so that their united surface is convex backwards.

The pisiform is the smallest of the bones and is a little round bone resting entirely on the palmar surface of the cuneiform; it, with the hook of the unciform, forms the projection on the ulnar side of the wrist; the tubercle of the scaphoid and ridge of the trapezium form the projection on the radial side of the wrist.

The unciform is distinguished by having a hook-like process on its palmar surface.

The proximal row of bones articulates above with the radius and triangular fibro-cartilage, and below with the distal row of bones. The distal row of bones articulates below with the five metatarsal bones; the first metatarsal with the trapezium; the other four fitted into the trapezoid, os magnum, and unciform.

Ossification

One centre for each bone appears after birth, and the carpus is usually completely ossified at puberty.