The elbow is a hinge joint, or a joint that only moves in one plane of direction. The three bones that make up the elbow are: the humerus (upper arm bone), the radius, and the ulna which enable the elbow to bend upward and straighten out.
Common elbow injuries occur when stress is put on the ligaments surrounding the elbow. This type of injury causes damage to the tissue around the elbow and to the bicep and triceps muscles.