(Also known as a Partial Dislocation)
The shoulder is the junction of three bones: the humerus (upper arm bone), the clavicle (collarbone), and scapula (shoulder blade). A group of four muscles and their respective tendons, known as the rotator cuff, connects the humerus to the shoulder socket, or glenoid, stabilizes the joint, and allows the upper arm to be lifted and rotated. In a subluxation, the humerus slips out of the glenoid cavity as a result of weakness in the rotator cuff or a blow to the shoulder area. A subluxation can occur in one of three types: anterior (forward), posterior (backward), and inferior (downward).
Causes and Risk Factors
Subluxation is most often caused by laxity or instability within the shoulder joint, which allow the head of the humerus to slip partially out of the glenoid.
Shoulder subluxation is often a recurrent problem caused by weakness in the rotator cuff or laxity in the tendons that stabilize the shoulder. Therefore, people with previous shoulder dislocation or subluxation stand at the highest risk for future subluxation. Wrestlers, basketball players and football players compose the biggest risk group. Twisting, lifting and hitting, as well as throwing sports, also pose a higher risk of injury of this type. Those with arthritis, degeneration of the rotator cuff, or poor muscle tone are also at great risk.
Last updated: Jan-01-00