Editorial Commentary: Does the Morphology of the Acromion Explain All Rotator Cuff Tears? 
Given the high prevalence of rotator cuff tears and their socioeconomic impact, surgeons and researchers have tried to understand their etiology and pathomechanism for almost hundred years.  Articles about tendon degeneration with increasing age dominate the literature, and numerous factors contributing to tendon degeneration have been identified.  One of them, the lateral extension of the acromion, as quantitated using the acromion index or the critical shoulder angle, has become very popular in the last few years.  Other big tendons in the human body, such as the distal biceps tendon, the Achilles tendon, or the patellar tendon, are also subject to degenerative changes, but they normally do not lose their continuity without a relevant trauma.  This raises 2 questions: What makes the rotator cuff different from the other tendons, and why are there not more rotator cuff tears related to a trauma?  What we do know is that risk factors for rotator cuff tear include trauma, dominant arm, and age, whereas the effect of a large acromion is more ambiguous.