Shoulder impingement syndrome, which is sometimes called swimmer’s shoulder or thrower’s shoulder, is caused by the tendons of the rotator cuff muscles becoming impinged as they pass through a narrow bony space. With repetitive pinching, the tendons become irritated and inflamed.
This can lead to thickening of the tendon which may cause further problems because there is very little free space, so as the tendons become larger, they are impinged further by the structures of the shoulder joint and the muscles themselves.
Impingement Syndrome in itself is not a diagnosis, it is a clinical sign. There are at least nine different diagnoses which can cause impingement syndrome which include bone spurs, rotator cuff injury, labral injury, shoulder instability, biceps tendinopathy and scapula dysfunction. If left untreated, shoulder impingement can develop into a rotator cuff tear.
The supraspinatus muscle is probably the most commonly involved in impingement syndrome of the shoulder.
Shoulder impingement is classified as internal or external depending on the causes with external impingement being divided into primary which is caused by a bony spur or some direct cause and secondary impingement which occurs as the result of poor stabilization of the shoulder joint.
Symptoms include pain which comes on gradually over a period of time. There will be pain at the front and side of the shoulder joint, especially during overhead movements such as in throwing, racket sports and swimming. There may be pain in the shoulder when the arm is held out to the side turned outwards (abduction and external rotation). Another give away sign of impingement is pain in an arc from about 70 degrees to 130 degrees when lifting the arm out sideways and up above the shoulder.