Medial Collateral Ligament (Elbow — UCL)

ligamentum collaterale ulnare cubiti (full)

The medial collateral ligament (UCL) of the elbow has three components: the anterior bundle (primary valgus stabiliser — taut throughout flexion-extension), the posterior bundle (taut in flexion), and the transverse ligament. Valgus overload in overhead throwing athletes produces the repetitive stress that tears the anterior bundle, producing medial elbow pain with decreased velocity in pitchers. UCL reconstruction (Tommy John surgery) using a palmaris or gracilis graft achieves return-to-sport at the same level in 80% of professional pitchers.

Region: Upper Arm

Anatomical Data

Origin, Insertion & Supply

Origin	Inferior medial epicondyle
Insertion	Medial coronoid process (anterior bundle) and olecranon (posterior bundle)

Biomechanics

Function & Actions

Actions	Primary valgus stabiliser of the elbow; the anterior bundle is most important and is reconstructed in Tommy John surgery

Clinical Relevance

Clinical Notes

UCL insufficiency is assessed by the moving valgus stress test (valgus stress applied during rapid elbow flexion from 120 to 70 degrees reproduces medial elbow pain at 70-120 degrees of flexion). MRI arthrography with intraarticular gadolinium is the gold standard — the T-sign (contrast passing through the UCL into the medial joint space) confirms complete tear. Tommy John surgery requires 12-18 months rehabilitation.

Pathology

Common Injuries & Conditions

UCL Tear in Throwing Athletes (Tommy John)

Anterior bundle UCL rupture from valgus overload in pitchers producing medial elbow pain and velocity loss managed with UCL reconstruction and 12-18 month rehabilitation.