The shoulder is made up of three bones: The upper arm bone (humerus), the shoulder blade (scapula), and the collarbone (clavicle). The shoulder is a ball-and-socket joint: the ball, or head, of the humerus fits into a shallow socket (glenoid) in your shoulder blade.

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 your arm. Your rotator cuff also helps to secure the humeral head within the shoulder socket.

There is a lubricating sac called a bursa between the rotator cuff and the bone on top of your shoulder (acromion). The bursa allows the rotator cuff tendons to glide freely when you move your arm. When the rotator cuff tendons are injured or damaged, this bursa can also become inflamed and painful.

In calcific tendonitis, deposits of calcium form in the tendons of the rotator cuff. The area around the calcium deposit may become very inflamed causing pain and weakness of the shoulder.
It is a common condition which occurs usually between the ages of 30 – 60 years old and more often in females. It can occur in both shoulders but it is more commonly found in the dominant arm and it may re-occur after surgical or non-surgical management.

The exact cause of the calcium deposits is unknown, however, various theories have been proposed. It is believed that a poor oxygen supply to the tissues of the rotator cuff tendon lead to calcium production. A poor oxygen supply may be precipitated by age, smoking, ‘wear and tear’ or increased pressure on the tendon.