One of the most common causes of shoulder pain is the result of a [no-glossary]torn rotator cuff[/no-glossary].

The rotator cuff is made up of 4 [no-glossary]muscles[/no-glossary]. Their tendons form a "cuff" of tissue over the upper end of the arm bone ([no-glossary]humerus[/no-glossary]) — the rounded "ball" at the top of the ball and socket joint. The space between the rotator cuff and the shoulder blade (scapula) is cushioned and lubricated by bursae.

The rotator cuff helps you move your arm in a circular fashion:

• swimming
• throwing a ball
• lifting an item overhead
• putting on a jacket

One of these [no-glossary]muscles[/no-glossary] (called the supraspinatus) rests on top of your shoulder. Its tendon travels under the shoulder blade, on the outside of the shoulder — a position that makes it vulnerable to injury. The injury can lead to inflammation of the tendon (tendinitis) or the nearby bursae (bursitis).

Torn rotator cuffs also are associated with what is called shoulder impingement syndrome, a squeezing or pinching of the rotator cuff.

Sometimes a rotator cuff tears completely. In other cases, there is only a partial tear.