The shoulder is surrounded by four muscles and tendons giving it stability. They are commonly known as the rotator cuff. The rotator cuff is enclosed in a fluid filled sac or bursa, which helps the tendon to slide friction free. The rotator cuff is open to injury and degeneration.

If the small space in between the rotator cuff and the bone above it becomes narrowed, the rotator cuff tendons and bursa can become squeezed, causing pain. This can lead to inflammation in the joint and may lead to tendonitis and bursitis. This is called impingement.

Calcification of the tendon (calcify tendonitis) can occur in the rotator cuff causing acute inflammation and pain. Calcification of the rotator tendon can be usually diagnosis with an x-ray.
Normally under orthopaedic examination, if a patient is unable to lift their arm above their shoulder, this is called painful arch. An arch refers to the range of movement of a healthy shoulder normally 180 degrees. The rotator cuff is susceptible to aging, as we get older the rotator cuff goes through a degenerative changes, commonly known as a rotator cuff tear but in fact is more of a wearing and thinning of the rotator cuff.