The rotator cuff is a group of four muscles that come together as tendons to form a covering around the head of the humerus. The rotator cuff attaches the humerus to the shoulder blade and helps to lift and rotate arm. When one or more of the rotator cuff tendons is torn, the tendon no longer fully attaches to the head of the humerus.
There are different types of tears.
- Partial tear. This type of tear is also called an incomplete tear. It damages the tendon, but does not completely sever it.
- Full-thickness tear. This type of tear is also called a complete tear. It separates all of the tendon from the bone. With a full-thickness tear, there is basically a hole in the tendon.
If you fall down on your outstretched arm or lift something too heavy with a jerking motion, you can tear your rotator cuff.
Most tears are the result of a wearing down of the tendon that occurs slowly over time. This degeneration naturally occurs as we age. Rotator cuff tears are more common in the dominant arm. Several factors contribute to degenerative, or chronic, rotator cuff tears.
- Repetitive stress. Repeating the same shoulder motions, again and again, can stress your rotator cuff muscles and tendons. Baseball, tennis, rowing, and weightlifting are examples of sports activities that can put you at risk for overuse tears.
- Lack of blood supply. As we get older, the blood supply in our rotator cuff tendons lessens. Without a good blood supply, the body’s natural ability to repair tendon damage is impaired. This can ultimately lead to a tendon tear.
- Bone spurs. As we age, bone spurs (bone overgrowth) often develop on the underside of the acromion bone. When we lift our arms, the spurs rub on the rotator cuff tendon. This condition is called shoulder impingement, and over time will weaken the tendon and make it more likely to tear.