Ligament · Hand

Ulnar collateral ligament of the wrist

Ligamentum collaterale carpi ulnare

The checkrein on the little-finger side of the wrist. It descends from the styloid process of the ulna — the knob you can feel on that edge of the back of the wrist — and fans out to reach the triquetral and the pisiform, with some fibres carrying on into the flexor retinaculum. Its job is to stop the wrist tilting too far toward the thumb, the mirror image of the radial collateral ligament on the opposite side. It never works alone: it shares this corner of the wrist with the triangular fibrocartilage complex and the ulnocarpal ligaments, so it is one restraint in a dense overlapping set rather than a lone strap.