Shoulder dislocation occurs when the head of the humerus (upper arm bone) separates from the glenoid cavity (socket) of the scapula (shoulder blade). The shoulder joint, a highly mobile ball-and-socket joint, is stabilized by ligaments, the joint capsule, and rotator cuff tendons. While this design allows for a wide range of motion, it also makes the joint susceptible to dislocation.
The most frequent type, accounting for about 95% of cases, is an anterior dislocation. This typically happens when the arm is forced into an abducted (out to the side) and externally rotated position. During a dislocation, the structures stabilizing the shoulder joint are damaged. Factors such as the patient's age at the first dislocation, the extent of structural damage, and joint laxity significantly increase the risk of recurrent dislocations.
Symptoms include severe pain and an inability to move the affected arm, often accompanied by a visibly deformed or "empty" appearance in the shoulder region. Although anterior dislocations are most common, dislocations can also occur in other directions (posterior, inferior), albeit rarely. Shoulder dislocations can affect individuals of any age and may be associated with other injuries, such as fractures, or damage to nerves and blood vessels.