The shoulder is the most mobile and the most commonly dislocated large joint in the body. Dislocation means that the joint is moved out of position, such that the joint surfaces at the ends of the bones are no longer in contact. In the shoulder, most dislocations are anterior (moving forward from the body); however, they can occur in several directions. When a dislocation occurs, the soft tissues that stabilize the shoulder can be torn and the bone that forms the socket can also be broken at the same time.
Traumatic dislocations of the shoulder can result in a Bankart lesion (tear). The head of the humerus (ball of upper arm bone) is held in proper relation to the glenoid (socket of the shoulder joint) by the rotator cuff muscles, labrum, and ligaments. Ligaments run from the glenoid to the humeral head and they blend with fibrous tissue called the capsule that encloses the entire joint. When the humeral head is forced forward in a dislocation, the soft tissues stretch or tear. In some cases, bone is fractured off the glenoid rim, resulting in a bony Bankart lesion.
X-ray of a patient with a bony Bankart facture of the glenoid (socket), secondary to shoulder dislocation.
3-D scan of the same patient more clearly demonstrating the fracture.