Dorsal radio-ulnar ligament

At a glance

English

Dorsal radio-ulnar ligament

Latin (TA2)

Ligamentum radioulnare dorsale

System

Ligament

Region

Upper limb

Side

Paired, left and right

About the dorsal radio-ulnar ligament

At the wrist the radius rotates around the head of the ulna at the distal radio-ulnar joint. The bones meet where the rounded ulnar head fits a shallow concavity on the inner side of the lower radius, the ulnar notch. The fit is poor, and the joint depends on soft tissue for stability, above all on the triangular fibrocartilage complex. The dorsal radio-ulnar ligament is one of the two thickened margins of that complex, the one on the back of the wrist; the palmar radio-ulnar ligament is its partner on the front.

The ligament runs across the back of the joint from the dorsal rim of the radius's ulnar notch towards the ulna. It has superficial and deep fibres. The superficial fibres pass to the base of the ulnar styloid process, while the deep fibres attach in a pit at the base of the ulnar head next to the styloid, the fovea. Between the dorsal and palmar ligaments stretches the articular disc of the distal radio-ulnar joint, a triangular plate of fibrocartilage that separates the ulnar head from the carpal bones.

As the forearm turns, the two ligaments share the job of holding the radius to the ulna, and their roles change with position. In pronation, as the radius crosses over and the ulnar head shifts towards the back of the notch, parts of the dorsal ligament tighten, and in supination the palmar fibres take more load; the superficial and deep fibres behave in opposite ways, which is why accounts differ on which band is tight when.

A fall on the outstretched hand or a forced twist can tear the ligament, often together with a fracture of the lower radius or of the ulnar styloid. The result is a painful, unstable distal radio-ulnar joint in which the ulnar head becomes prominent on the back of the wrist and clicks with rotation. Arthroscopic or open repair of the foveal attachment may be needed.

Attachments and function

Attaches from

The back rim of the radius's ulnar notch.

Attaches to

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

Function

Stabilises the back of the distal radio-ulnar joint and, with the palmar ligament, holds the radius to the ulna as the forearm rotates.

Nerve supply

The posterior interosseous nerve, with branches of the anterior interosseous nerve.

Blood supply

Dorsal branches of the anterior and posterior interosseous arteries.