Rotator cuff tendinitis is an inflammation (irritation and swelling) of the tendons of the shoulder.

The shoulder joint is a ball and socket type joint where the top part of the arm bone (humerus) forms a joint with the shoulder blade (scapula). The rotator cuff holds the head of the humerus into the scapula.

Inflammation of the tendons of the shoulder muscles can occur in sports requiring the arm to be moved over the head repeatedly as in tennis, baseball (particularly pitching), swimming, and lifting weights over the head. Chronic inflammation or injury can cause the tendons of the rotator cuff to tear.

The risk factors are being over age 40 and participation in sports or exercise that involves repetitive arm motion over the head (such as baseball).

• Pain associated with arm movement
• Pain in the shoulder at night, especially when lying on the affected shoulder
• Weakness with raising the arm above the head, or pain with overhead activities (brushing hair, reaching for objects on shelves, etc.)

A physical examination will reveal tenderness over the shoulder. Pain may occur when the shoulder is raised overhead. There is usually weakness of the shoulder when it is placed in certain positions.

X-rays may show a bone spur, while MRI may demonstrate inflammation in the rotator cuff. If a tear in the rotator cuff is present, this can usually be identified on MRI.