The anatomy of the shoulder joint allows for a great range of motion. Accordingly, there is not much inherent stability in this joint. The shoulder is composed of three bones, the scapula (shoulder blade), the humerus (upper arm) and the clavicle (collarbone). The rotator cuff is composed of the tends of the four muscles that span this joint. They include the supraspinatous, infraspinatous, teres minor and subscapularis. The rotator cuff connects the humerus to the scapula and helps to keep the head of the humerus in the shoulder joint. The portion of the scapula that makes the roof of the shoulder joint is called the acromion. There is a bursa, or lubricated sack of tissue that sits between these structures. Usually, there is enough room between the rotator cuff and the acromion to allow for the tendons to slide under them when the arm is raised. Sometimes, irritation and swelling occurs in these tissues. Raising the arms leads to rubbing ad pinching. This is the shoulder impingement syndrome.
Causes of Shoulder Impingement Syndrome
Shoulder impingement syndrome develops when there is an inadequate amount of room between the acromion, or roof of the shoulder joint and the rotator cuff tendons. This may be caused by irritation and swelling of the tendons or the bursa. Bone spurs may develop which can further decrease the amount of room the bursa and tendons have underneath the acromion. Wear and tear between the scapula and the collar bone can lead to bone spurs. Spurs in this location also can produce shoulder impingement. Repetitive activities involving lifting the arms overhead can produce this syndrome.
Signs and Symptoms of Shoulder Impingement Syndrome
Generalized aching in the shoulder is an early sign of shoulder impingement syndrome. The pain may be worse during sleep. A sharp pain may occur when trying to reach into your back pocket. The joint gradually becomes stiffer. Pain, weakness and difficulty raising the arm may occur.
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Medical Content Last Updated on 07/12/2008
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