The elbow-joint is a ginglymus or hinge joint. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm. The bony prominence at the very tip of the elbow is the olecranon process of the ulna. Movements Two main movements are possible at the elbow: · The hinge-like bending and straightening of the elbow (flexion and extension) happens at the articulation ("joint") between the humerus and the ulna. · The complex action of turning the forearm over (pronation or supination) happens at the articulation between the radius and the ulna (this movement also occurs at the wrist joint). In the anatomical position (with the forearm supine), the radius and ulna lie parallel to each other. During pronation, the ulna remains fixed, and the radius rolls around it at both the wrist and the elbow joints. In the prone position, the radius and ulna appear