Attrition sign in impingement syndrome.

Extrinsic compression of the rotator cuff by the coracoacromial arch has been accepted as a major factor in the etiology of bursitis, cuff tendonitis, and rotator cuff tears. Other etiologies for rotator cuff syndrome have also been proposed in various patient populations. These include repetitive microtrauma and underlying instability with tensile overload, particularly in the younger (younger than 35) athletic population.