Shoulder pain is a common complaint shared by people of all ages and activity levels. By far the most common diagnosis, shoulder impingement syndrome accounts for 44-65% of all shoulder complaints.
When the arm is raised to shoulder height and above, the space between the roof of the shoulder (acromion) and the upper arm bone (humeral head) narrows. This space contains the muscles of the shoulder (rotator cuff) and a sac of lubricating fluid (bursa). Shoulder impingement occurs when the rotator cuff and bursa get pinched between the two bones as the arm is raised, leading to irritation and pain.