UCLs

Ulnar collateral ligaments (UCLs) are the medial stabilizing structures of the elbow. The UCL complex consists of three bands: the anterior oblique ligament, the posterior oblique ligament, and the transverse ligament. The anterior oblique ligament is the primary restraint to valgus stress across much of the elbow’s range of motion, with the other bands contributing to stability, especially at higher degrees of flexion.

Anatomically, the UCL runs from the medial epicondyle of the humerus to the sublime tubercle on the ulna, forming part of the medial collateral ligament complex. It works in concert with the flexor-pronator muscle group to stabilize the elbow during throwing and other overhead activities.

Clinically, UCL integrity is critical for athletes who perform repetitive throwing, such as baseball pitchers, as well as for joints subjected to valgus stress in daily activities. Deterioration or acute injury to the UCL can cause medial elbow pain, decreased throwing velocity, and instability.

Injury to the UCL often results from repetitive microtrauma or a single acute tear. Diagnosis relies on history and physical examination with tests that stress valgus stability, and imaging such as magnetic resonance imaging (MRI) or dynamic ultrasound to assess ligament integrity.

Treatment ranges from nonoperative management—rest, physical therapy focusing on the forearm flexor-pronator complex, and a gradual throwing progression—to surgical reconstruction or repair in high-demand athletes. The common reconstruction, often called Tommy John surgery, uses a graft (commonly from the palmaris longus or gracilis) to recreate the UCL, followed by a structured rehabilitation program. Return to competitive throwing typically occurs about 12 to 18 months after surgery.