Internal impingement syndromes of the shoulder

The internal impingement syndromes are a group of conditions that result from the impingement of the soft tissues of the rotator cuff and joint capsule on the glenoid or between the glenoid and the humerus. They should not be confused with conditions where impingement of cuff and bursa occur on the structures of the coracoacromial arch, so-called external impingement. Some controversy surrounds the true etiology of the soft tissue injuries seen in internal impingement syndromes and whether they are truly the result of impingement. Internal impingement seems to be a normal physiological occurrence with the shoulder in certain positions. Imaging findings in these conditions include undersurface partial-thickness cuff tears, superior labral pathology, and bone changes.