Calcific Tendonitis, as the name suggests, is the deposition of calcium in the rotator cuff of shoulders. Rotator Cuff is a group of muscles and tendons that surround the shoulder joint. When there is build up of calcium, it puts pressure on the rotator cuff which causes inflammation and pain. In fact, it is one of the worst pains in the shoulder. This calcium deposit also reduces the space between rotator cuff and the acromion (acromion is a bony process on the shoulder blade, scapula). This affects the normal functioning of rotator cuff thus creating a subacromial impingement between the acromion and the calcium deposit in the rotator cuff, while lifting the arm overhead. This condition is quite common and generally affects people over the age of 40.