A dislocation of the shoulder joint happens when the bones making up your shoulder joint are moved apart so that the joint no longer functions.
Your shoulder is made up of two bones: the ball (humerus) and the socket (part of your shoulder blade). When the ball part of the joint is dislocated in front of the socket, it is called an anterior dislocation. When it is dislocated behind the socket, it is called a posterior dislocation. In severe cases, ligaments, tendons, and nerves also can be stretched and injured.