The sulcus sign is an examination to determine the extent and/or presence of inferior instability of the glenohumeral joint. This test can be administered with the patient either seated or standing with his arm relaxed at her side. The examiner palpates the shoulder by placing her thumb and fingers on the anterior and posterior aspects of the humeral head. The examiner grasps the patient's elbow with her other hand and applies a downward distraction force. A positive test will result in a sulcus being formed between the acromion and the humeral head as the humeral head moves inferiorly while the force is being applied.