The shoulder is a complex and dynamic joint that offers the widest range of motion of any joint in the human body. With this incredible mobility comes inherent instability due to the lack of bony constraint. The shoulder is dynamically stabilized through the rotator cuff, a group of muscles that act synergistically throughout the range of motion. These muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis (Fig. 1). Unfortunately, they are prone to tearing near their tendinous insertions, generally due to age-related degenerative changes, trauma, subacromial impingement, and repetitive stresses. Injury to the rotator cuff accounts for nearly 50% of all major shoulder injuries and is highly prevalent in people aged 60 years or older (Murrell and Walton, 2001).
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