An understanding of the normal magnetic resonance (MR) infrastructural
details of musculotendinous elements of the rotator cuff forms the ba
sis for analysis of its pathology. The muscular bellies of the teres m
inor, infraspinatus, supraspinatus, and subscapularis are easily ident
ified in MR images. In their lateral course both the supraspinatus and
infraspinatus muscles transition to tendons gradually. Their lateral
tendinous portions partially overlap and form a layered appearance on
MR images. The subscapularis, with its fan-like tendinous insertional
slips at the lesser tuberosity, can be identified easily in all imagin
g planes. The ligamentous structures of the shoulder, including the co
racoacromial and coracohumeral ligaments, are visualized as low signal
bands in all imaging planes. The capsuloligamentous structures includ
ing the superior, middle, and inferior glenohumeral ligament and gleno
id labrum present considerable anatomic variations. This is especially
true with respect to the anterior labrum, which varies from absent to
a well-formed triangular appearance. Understanding the basic MRI anat
omy of all soft tissue structures of the shoulder is essential for app
ropriate interpretation of lesions related to the shoulder.