In summary, rotator cuff pathology is a continuum that begins with degeneration of collagen fibers at a rate that exceeds that of repair. The degenerative process is accelerated with aging, chronic inflammatory diseases, impingement, and repetitive activity. A tendon weakened by disease may then be torn by routine physical activity. MR imaging can help predict which patients are at risk for rotator cuff disease because of abnormal anatomy and can detect the disease at an early stage so that the progression may be altered before a tear occurs.