Subacromial Impingement Syndrome is the inflammation and irritation of the rotator cuff tendons as it passed through a small passageway called the subacromial space. This results in pain when taking the arm out to the side, a reduced range of motion and weakness within the shoulder joint.
Irritation of the tendon can be caused by several mechanisms such as degeneration and anatomical variations. The most common is overuse of the shoulder, leading to microtrauma of the tendon and associated inflammation in the area. This reduces the amount of space for the tendon to pass through, creating friction between the surrounding bony landmarks.