Humeral avulsion of the glenohumeral ligament: The J sign

Abstract

The lesion resulting from humeral avulsion of the glenohumeral ligament (HAGL) is an important cause of anterior glenohumeral instability and can be seen in isolation or combination with an antero-inferior labral complex lesion. A conclusive magnetic resonance imaging diagnosis is aided when either a joint effusion is present or a contrast arthrography of the shoulder is  performed.It is important to be familiar with the J sign as it represents contrast leaking through the defect in the lateral attachment of the joint capsule.