Shoulder subluxation / dislocation is characterized by the failure of the shoulder joint to remain in its proper position. Specifically, it is characterized by the separation of the humerus (upper arm bone) from the scapula (the bone connecting the humerus to the collar bone). If the joint slides partially out of place, this is called shoulder subluxation. If it slides completely out of place, shoulder dislocation has taken place. This type of injury can lead to a long term condition known as shoulder instability in which the shoulder joint is unable to remain permanently in its proper position. This is because shoulder dislocation can damage the ligaments of the shoulder and thus adversely affect their ability to hold the joint in place. A shoulder support or arm sling can treat this condition by restricting the movement of the shoulder joint and allowing those ligaments to heal.