This condition, also known as scapulocostal or scapulothoracic syndrome, occurs when the scapula catches on the muscles or bones of the chest wall. Instead of gliding smoothly across the chest wall as the arm is used, the scapula catches and grinds.

This condition can be caused by repetitive motions that lead to inflammation or atrophy of the muscles beneath the scapula. It can also be caused by a fracture that changes the shape of the scapula, or an injury to the ribcage that results in a rib sticking out from its normal position.

Symptoms can include sounds or sensations of grinding, popping, catching and thumping as the arm is moved. It may cause pain, or it may be painless.

Treatment options may include rest, ice, anti-inflammatory medications, cortisone injections, and physical therapy. If those treatments are unsuccessful, surgery may be needed to change the shape of the scapula.