The normal shoulder: common variations that simulate pathologic conditions at MR imaging

The appearance of the supraspinatus tendon and anterior capsular mechanism was analyzed in 60 asymptomatic shoulders with magnetic resonance (MR) imaging. The images were reviewed with special attention to findings that simulate pathologic conditions, as defined by means of currently accepted criteria. On T1-weighted and proton-density (PD) spin-echo (SE) images, intermediate signal intensity was present within the supraspinatus tendon in most shoulders. Focal signal intensity within the distal tendon was particularly common finding, being present in 95% (57 of 60) of shoulders on PD images. Focal obliteration of the subacromial-subdeltoid fat stripe and acromioclavicular joint arthrosis were seen in 95% (57 of 60) and 48% (29 of 60) of the subjects, respectively. There was considerable variation in the shape of the anterior glenoid labrum-glenohumeral ligament (GHL) complex. The labrum may appear triangular, round, crescentic, or absent. The middle and inferior GHLs lie in proximity to the upper half of the anterior labrum; the cleavage plane between the ligaments and the labrum can mimic a tear at MR imaging.