CausesBy Mayo Clinic staff
Four major muscles (subscapularis, supraspinatus, infraspinatus and teres minor) and their tendons connect your upper arm bone (humerus) with your shoulder blade (scapula). A rotator cuff injury, which is fairly common, involves any type of irritation or damage to your rotator cuff muscles or tendons, including:
- Tendinitis. Tendons in your rotator cuff can become inflamed due to overuse or overload, especially if you're an athlete who performs a lot of overhead activities, such as in tennis or racquetball.
- Bursitis. The fluid-filled sac (bursa) between your shoulder joint and rotator cuff tendons can become irritated and inflamed.
- Strain or tear. Left untreated, tendinitis can weaken a tendon and lead to chronic tendon degeneration or to a tendon tear. Stress from overuse also can cause a shoulder tendon or muscle to tear.
Common causes of rotator cuff injuries include:
- Normal wear and tear. Increasingly after age 40, normal wear and tear on your rotator cuff can cause a breakdown of fibrous protein (collagen) in the cuff's tendons and muscles. This makes them more prone to degeneration and injury. With age, you may also develop calcium deposits within the cuff or arthritic bone spurs that can pinch or irritate your rotator cuff.
- Poor posture. When you slouch your neck and shoulders forward, the space where the rotator cuff muscles reside can become smaller. This can allow a muscle or tendon to become pinched under your shoulder bones (including your collarbone), especially during overhead activities, such as throwing.
- Falling. Using your arm to break a fall or falling on your arm can bruise or tear a rotator cuff tendon or muscle.
- Lifting or pulling. Lifting an object that's too heavy or doing so improperly — especially overhead — can strain or tear your tendons or muscles. Likewise, pulling something, such as a high-poundage archery bow, may cause an injury.
- Repetitive stress. Repetitive overhead movement of your arms can stress your rotator cuff muscles and tendons, causing inflammation and eventually tearing. This occurs often in athletes, especially baseball pitchers, swimmers and tennis players. It's also common among people in the building trades, such as painters and carpenters.
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