The posterior band of the ulnar collateral ligament (posterior oblique ligament) is the thickened posterior capsule of the elbow running from the medial epicondyle to the olecranon's medial aspect. It becomes taut in elbow flexion and contributes to stability against valgus stress and posterior rotatory instability at 90-120 degrees flexion, complementing the anterior band which is tightest in extension.
Provides valgus stability at elbow flexion angles of 90-120 degrees, resists posterior rotatory instability, and contributes to the posterior joint capsule integrity.
The posterior UCL band is stressed during the late cocking and acceleration phases of throwing, where the elbow is flexed to 90 degrees and maximum valgus torque is applied. Its injury in overhead athletes produces posterior-medial elbow pain at 90 degrees flexion distinct from anterior UCL injury at extension. In UCL reconstruction (Tommy John surgery) for throwing athletes, the anterior band is the primary target, but posterior band integrity affects elbow stability throughout flexion arcs and influences rehabilitation protocols.
Repetitive valgus loading at 90-120 degrees elbow flexion during throwing stresses the posterior UCL band, producing posterior-medial elbow pain at maximal cocking; MRI with arthrogram in elbow flexion differentiates posterior from anterior band pathology and guides whether reconstruction or rehabilitation is the preferred treatment.
