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.