Shoulder impingement, or swimmer’s shoulder, is a musculoskeletal condition that causes shoulder pain. It occurs when your rotator cuff catches or rubs against the acromion, or the topmost part of your shoulder. Then, the space between the rotator cuff and acromion constricts, creating more pressure. The increased pressure can, in turn, cause a shoulder impingement.
Overuse is the most common cause of shoulder impingement. For instance, you have a higher risk of getting inflamed tendons if you use your shoulder repeatedly for certain activities. But sometimes, the cause of swimmer’s shoulder is unknown.