[MR imaging of the shoulder. Impingement and instability-related abnormalities].

In addition to the case history and the clinical examination, MR imaging has an important role in the diagnosis and differential diagnosis of numerous shoulder abnormalities and in the investigation of chronic shoulder pain. Important indications for MR imaging are any conditions or symptoms making assessment of the rotator cuff and the labrocapsular complex necessary. Assessment of the rotator cuff muscles, in particular, is crucial. The value of MR arthrography, which is still controversial, is discussed. The greatest potential benefit of MR arthrography is the accurate evaluation of subtle rotator cuff abnormalities and shoulder instability-related lesions, and the assessment of pathologic conditions of the long biceps tendon. This paper describes the most common pathologic findings of the shoulder joint and describes how the relevant findings are reported and quantified for the orthopaedic shoulder surgeon.