Distal radioulnar joint

The distal radioulnar joint is a pivot-joint formed between the head of the ulna and the ulnar notch on the lower end of the radius. The articular surfaces are connected together by the following ligaments:

• Articular disc
• The Volar Radioulnar Ligament (anterior radioulnar ligament) —This ligament is a narrow band of fibers extending from the anterior margin of the ulnar notch of the radius to the front of the head of the ulna.
• The Dorsal Radioulnar Ligament (posterior radioulnar ligament) —This ligament extends between corresponding surfaces on the dorsal aspect of the articulation.

The synovial membrane of this articulation is extremely loose, and extends upward as a recess (recessus sacciformis) between the radius and the ulna.

Movements.—The movements in the distal radioulnar articulation consist of rotation of the lower end of the radius around an axis which passes through the center of the head of the ulna. When the radius rotates forward, pronation of the forearm and hand is the result; and when backward, supination. It will thus be seen that in pronation and supination the radius describes the segment of a cone, the axis of which extends from the center of the head of the radius to the middle of the head of the ulna. In this movement the head of the ulna is not stationary, but describes a curve in a direction opposite to that taken by the head of the radius. This, however, is not to be regarded as a rotation of the ulna—the curve which the head of this bone describes is due to a combined antero-posterior and rotatory movement, the former taking place almost entirely at the elbow-joint, the latter at the shoulder-joint.