Figure 4. With the transducer placed over the long axis of the deltoid muscle (D), note the longitudinal striations (upper arrows) of the fibrofatty septa in between the muscle bundles. Supraspinatus tendon (S) is displayed in its long axis deep to the deltoid. The tendon rests on the bright echogenic surface of the proximal humerus. The humeral head shows on the medial aspect (observer’s right) and the greater tuberosity more laterally. The anatomic neck is recognized on the groove (lower arrow) between these bone surfaces.