This occurs when the rotator cuff tendons collide or strike against the roof of the shoulder (Acromion) formed by a part of the shoulder blade bone (Scapula).
A small space between the roof of the shoulder and the top of the arm bone contains the rotator cuff tendons. This space is further reduced during overhead activities such as painting, swimming, tennis and other overhead activities. This can lead to damage to the rotator cuff tendon in the form a tendinosis (damage of tendons at a cellular level) or even a tear. This will cause the bursa (a normal tissue between the rotator cuff and the roof of the shoulder to prevent friction) to become inflamed and cause pain. Hence people who do a lot of overhead related activities are prone to develop this condition.
It can also be a result of wear and tear of the acromioclavicular joint (the joint at the roof of the shoulder and the collar bone) which can cause bony spurs to form and reduce the space for the rotator cuff tendons to glide. It can also be seen in people who have a slightly curved acromion, which is a common condition, which again reduces the space between the top of the arm bone and the roof of the shoulder.
Pain in the shoulder is the main symptom, particularly on overhead activities. This pain can also cause disturbed sleep particularly when lying on the affected shoulder. Weakness and inability to lift the arm may indicate a tear of the rotator cuff tendons. Limitation of shoulder movement due to pain may further lead to stiffness.
- X-rays can reveal bony spurs and degeneration of the acromioclavicular joint. Sometimes changes due to chronic impingement syndrome can also be seen in the bones.
- An MRI can be done to rule out a tear of the rotator cuff tendons
- A simple test wherein a local anaesthetic is injected into the sub-acromial space can be done to confirm that the pain is arising from the sub-acromial space