Palmar radio-ulnar ligament

At a glance

English

Palmar radio-ulnar ligament

Latin (TA2)

Ligamentum radioulnare palmare

System

Ligament

Region

Upper limb

Side

Paired, left and right

About the palmar radio-ulnar ligament

The distal radio-ulnar joint lets the lower radius swing around the head of the ulna during pronation and supination. Its bony surfaces, the convex ulnar head and the shallow notch on the radius that receives it, fit loosely, so the joint is held together mainly by the triangular fibrocartilage complex. Its thickened front margin is the palmar radio-ulnar ligament; the dorsal radio-ulnar ligament forms its back margin.

The ligament is a narrow, firm band that runs across the palmar side of the joint. It arises from the anterior rim of the ulnar notch and passes medially to the ulna. Like its dorsal partner it has two layers: superficial fibres reach the base of the ulnar styloid process, and deep fibres insert into the fovea, a small pit at the base of the ulnar head. Stretched between the two ligaments is the articular disc, the triangular plate of fibrocartilage that caps the ulnar head and separates it from the lunate and triquetrum. Fibres of the ulnolunate and ulnotriquetral ligaments arise from the front of the palmar ligament and run down to the carpus.

The palmar and dorsal ligaments work as a pair to stop the radius pulling away from the ulna. Their tension shifts as the forearm turns, so that between them the joint stays congruent from full pronation to full supination. The palmar ligament also acts as a base for the ulnar-side carpal ligaments, linking forearm stability with the wrist.

Injury to the ligament, often as part of a tear of the triangular fibrocartilage complex after a fall or forced rotation, leaves the joint unstable. Patients describe ulnar-sided wrist pain, weakness of grip and clicking on turning the forearm. When the deep foveal fibres are detached, reattachment to the ulna is usually needed to restore stability.

Attachments and function

Attaches from

The front rim of the radius's ulnar notch.

Attaches to

The ulnar head, at the fovea and the base of the ulnar styloid process.

Function

Stabilises the front of the distal radio-ulnar joint and, with the dorsal ligament, keeps the radius applied to the ulna in rotation.

Nerve supply

The anterior interosseous nerve, with twigs from the ulnar nerve.

Blood supply

Palmar branches of the anterior interosseous and ulnar arteries.