What is it?
Shoulder impingement syndrome is caused by pinching of the supraspinatus tendon (at the top of the rotator cuff) and bursa (lubricating sac) between the upper arm bone (humerus) and the acromion, the bony arch which is part of the scapula (shoulder blade) that forms the roof of the shoulder. The bursa functions as a cushion and low friction surface which allows the rotator cuff tendons to slide smoothly under the acromion.
Symptoms include pain at the front and/or outside of the shoulder and upper arm, and pain at night when sleeping on the affected side. Pain can often be brought on by lifting or elevating the arm, known as a painful arc. People sometimes describe a sharp pain brought on by reaching into their back pocket or above their heads.
Insufficient room between the acromion and the rotator cuff can cause impingement. Normally, the rotator cuff tendons can easily slide under the acromion each time your arm is raised; however, it is normal to have some degree of rubbing or pinching of the tendons and bursa. Overuse of the shoulder in an elevated position can cause the impingement to become a problem and can lead to ongoing pain or damage to the rotator cuff tendons.
Bony spurs on the undersurface of the acromion can contribute to an impingement syndrome, and the inflammation associated with a rotator cuff tear can also cause impingement pain. Poor posture and tight anterior chest wall muscles (pectoral muscles) can also contribute to an impingement syndrome.
Rest from the aggravating activites, ice, anti-inflammatory medicines and physical therapy are the mainstay of treatment. In particular, improving overall posture, as well as the position and stability of the shoulder blade is important as this will open up the space between the acromion and reduce the change of impingement. Corticosteroid injections or surgery may be needed in severe cases.