The Structural Anatomy of the Elbow
Biomechanically the elbow is relatively straightforward since it has only this one simple motion. Two other joints however can be considered as part of the elbow complex. The two bones in the forearm run parallel to each other when the palm is face up and they cross when the palm is face down. They articulate with each other at either end at the proximal and distal radioulnar joints. Although the distal radioulnar joint is closer to the wrist it is considered part of the elbow complex because it is closeley related functionally to the proximal joint.
At the proximal radioulnar joint, near the elbow, the relatively small head of the radius fits into the radial notch of the ulna, a small concavity on its lateral side. Attached to either side of the radial notch the annular ligament encircles the radial head like a ring keeping it in place and allowing it to swivel as the radius crosses the ulna.
At the other end of these bones near the wrist is the distal radioulnar joint. This time the ulna is relatively smaller and it's head fits into the ulnar notch of the radius. A structure called the articulating disk connects the two bones and seperates them from the wrist.
Because most of the muscles that control the wrist and hand originate at the elbow the great majority of elbow conditions can be traced to their overuse. The description of the biomechanics of the wrist and hand explains how these muscles are used.