increased from 13% in the youngest group (aged 50–59 y) to 20% (aged 60–69 y), 31% (aged 70–79 y), and 51% in the oldest group (aged 80–89 y). Some risk factors such as increased age and height cannot be changed. Increased body mass index is also associated with tearing. Recurrent lifting and overhead motions are at risk for rotator cuff injury as well. This includes jobs that involve repetitive overhead work, such as carpenters, painters, custodians, and servers. People who play sports that involve overhead motions, such as swimming, water polo, volleyball, baseball, tennis, and American football quarterbacks, are at a greater risk of experiencing a rotator cuff tear. Striking-based combat sports, such as boxing, also account for severe rotator cuff injuries of competitors, typically when their punches miss the target, or overusing the shoulder by throwing excessively large amounts of punches. Certain track-and-field activities, such as shot put, javelin throw are also of considerable risk, especially when performing outdoors under cold weather conditions or neglecting warming-up procedures, for proper warm-up of the throwing and/or swinging arm can help reduce the stress on the musculature of the shoulder girdle. Corticosteroid injections around the tendons increases the risk of tendon tear and delay tendon healing. Mechanisms of injury The shoulder is a complex mechanism involving bones, ligaments, joints, muscles, and tendons. The two main causes are acute injury or chronic and cumulative degeneration of the shoulder joint. Mechanisms can be extrinsic, intrinsic or a combination of both. The cuff is responsible for stabilizing the glenohumeral joint to allow abduction and rotation of the humerus. When trauma occurs, these functions can be compromised. Because individuals are dependent on the shoulder for many activities, overuse can lead to tears, with the vast majority being in the supraspinatus tendon. The role of the supraspinatus is to resist downward motion, both while the shoulder is relaxed and carrying weight. Supraspinatus tears usually occurs at its insertion on the humeral head at the greater tubercle. Though the supraspinatus is the most commonly injured tendon in the rotator cuff, the other three can also be injured at the same time. Acute tears The amount of stress needed to acutely tear a rotator cuff tendon will depend on the underlying condition of the tendon. If healthy, the stress needed will be high, such as with a fall on the outstretched arm. This stress may occur coincidentally with other