This proximal radioulnar jointis a trochoid or pivot-joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament.
The articulation of the radius with the ulna is effected by ligaments which connect together the extremities as well as the bodies of these bones. The ligaments may, consequently, be subdivided into three sets: 1, those of the proximal radioulnar articulation; 2, the middle radioulnar ligaments; 3, those of the distal radioulnar articulation.
Movements.—The movements allowed in this articulation are limited to rotatory movements of the head of the radius within the ring formed by the annular ligament and the radial notch of the ulna; rotation forward being called pronation; rotation backward,supination. Supination is performed by the Biceps brachii and Supinator, assisted to a slight extent by the Extensor muscles of the thumb. Pronation is performed by the Pronator teres and Pronator quadratus.