There are three radioulnar joints. The distal joint involves the concave distal radius articulating with the convex distal ulna and is not palpable directly. The middle joint involves the radial and ulnar shafts stabilized with an interosseous membrane - it is not palpable from the bodyís surface. The proximal joint involves the convex head of the radius rotating with the stable concave ulna.
With the patient relaxed, gently press the fingers and thumb of one hand on the distal radius and the fingers and thumb of the other hand on the distal ulna. Sense movement in these bones as both move when the patient is guided to pronate and supinate the forearm with the hand free to move. Sense greater movement with the hand planted on a stable surface while the forearm and arm and even trunk rotate around the planted hand, producing radioulnar pronation and supination. Radioulnar movement with the planted hand involves rotation of the ulna around a stabilized radius and occurs because of the presence triangular disk between the ulna and the carpal bones of the hand..