Three bones are engaged in the formation of this joint - the humerus above, the radius below, and the ulna behind. It has two lateral ligaments passing from the humerus to the radius. The outer one is the stronger and shorter of the two; the inner, the longer and smaller. It has also a capsular ligament of considerable extent, lined by synovial membrane. It is essentially hinge-like in its action, and admits only of movements of flexion and extension (fig. 353)