Tendonitis is an inflammation of the shoulder tendons. The signs of inflammation are pain, warmth, redness, tenderness to touch, and loss of function. Shoulder tendonitis (often called Rotator Cuff Tendonitis) can occur when the rotator cuff is overloaded, fatigued, traumatized, and with age-related degenerative changes. Pinching or impingement of the rotator cuff tendons occurs in a region under a bony structure called the acromion (the projection of the shoulder blade that forms the tip of the shoulder). Impingement happens when the arm is raised overhead repeatedly, or raised overhead with a heavy load in your hand, or may occur when you sleep on your shoulder. X-rays may show a hook or spur that increases the odds that you will pinch the rotator cuff tendons.
Treatment for impingement or rotator cuff tendonitis usually involves rest, anti-inflammatory medications like ibuprofen, physical therapy to restore proper strength and movement, and less often, a cortisone injection.