MR imaging of the elbow: normal variant and potential diagnostic pitfalls of the trochlear groove and cubital tunnel.

The proximal portion of the ulna includes the olecranon and the coracoid process, which together form the trochlear groove that articulates with the distal humerus. The groove is constricted at the junction of the olecranon and the coracoid process. A thin, transverse, nonarticular ridge intersects the groove at this junction. Both the constriction of the groove and the nonarticular ridge may simulate disease on MR imaging of the elbow.