Bone · Hand

Pisiform

Os pisiforme

A pea-sized bone that is not really part of the wrist's load-bearing structure at all. It is a sesamoid, formed within the tendon of flexor carpi ulnaris, and it sits on the palm-side face of the triquetral rather than between neighbours. You can feel it as the hard lump at the heel of the hand on the little-finger side, and unlike every other carpal it can be pushed gently from side to side, because it is anchored by tendon and ligament instead of being wedged in place. The flexor retinaculum, abductor digiti minimi and the pisohamate and pisometacarpal ligaments all attach to it, and the ulnar nerve and artery pass just to its thumb side.