The rotator cuff is a group of four small muscles in the shoulder. The muscles extend from the shoulder blade and attach into the top of the humerus (upper arm bone). These muscles have the important job of stabilising the shoulders ball and socket joint as well as helping the shoulder move smoothly in its extensive range of motion.

The shoulder is an extremely complex joint with a large range of motion. Because of the shoulders structure it is prone to injury and rotator cuff injuries are especially common. There are a number of causes of rotator cuff injuries.

1. Acute trauma to the shoulder such as a fall onto the shoulder or heavy weight lifting can cause an acute tear to the rotator cuff muscles.
2. Degenerative changes to the shoulder are also common. As people age or repetitively use their shoulders over time the rotator cuff muscle can degenerate and develop small tears. Small tears in the rotator cuff can cause weakness, pain and larger tears can develop over time.
3. Poor shoulder biomechanics. If people lift heavy weight or perform shoulder and upper body movements with poor mechanics repeatedly this can overload the small rotator cuff muscles and lead to injury.
4. Weakness in the rotator cuff is also a common cause of injury. The rotator cuff is responsible for stabilising the ball and socket joint while larger muscles such as the lats, traps, pecs and deltoid muscle are responsible for generating power at this joint. When the rotator cuff is weak it is still possible to generate power at the shoulder through the larger muscles but this creates power without stability. This can set in motion poor joint mechanics which can lead to pain and injury to the small muscles of the rotator cuff.

If there is pain and instability in the shoulder the first thing to do is to get a scan such as an MRI or ultrasound to see which muscles in the rotator cuff group are damaged. From here a treatment plan can be developed. In severe injuries surgery is often required but in minor tears rest and good rehab can be enough to get them sorted.

References

1. Economopoulos KJ, Brockmeier SF. Rotator cuff tears in overhead athletes. Clinics in sports medicine 2012 October 1; 31-4:675-692
2. http://www.sports-health.com/sports-injuries/shoulder-injuries/rotator-cuff-injuries