Kinematic MR imaging of the shoulder: normal patterns

We performed this study to define the normal patterns of the glenohumeral joint with kinematic MR imaging in healthy volunteers. Twenty healthy volunteers (39 shoulders) were studied with a 1.5-T imager. Successive fast low-angle shot images (75/11 [TR/TE], 15 degrees flip angle) were obtained in the axial plane from full internal to full external rotation at the superior, middle, and inferior glenoid levels. The free margin of the anterior labrum was seen to be slightly mobile and its base was always fixed. The anterior labrum showed changes in shape and signal intensity during internal rotation (54%). The posterior labrum remained motionless in 97% of patients and no shape or signal-intensity changes were noted during internal rotation. The anterior joint capsule was taut during external and internal rotation, exhibited a slack pattern in 51% of patients, and a folded pattern in 14% of patients. Kinematic MR imaging, which permits dynamic evaluation of the various anatomic components that may be involved in shoulder instability, also provides information on the labrocapsular ligamentous complex.