Sonographic assessment of ulno-humeral joint instability

The ulnar collateral ligament (UCL) of the elbow plays a crucial role in elbow stability, specifically as a valgus and rotational constraint. Injuries to the UCL are common in overhead-throwing athletes resulting in elbow instability. A timely diagnosis of early ulno-humeral joint space widening in the overhead-throwing athlete is required, to inform patient management and return to play. Sonographic assessment and measurement of the ulno-humeral joint space with and without stress, and comparison to the contralateral uninjured side provides a quantitative assessment of instability. A systematic sonographic technique for single operator stress ultrasound is outlined to improve consistency of assessment and reporting of findings.