The head of your upper arm bone, the humerus, fits into a rounded socket in your shoulder blade. This socket is called the glenoid. A shoulder dislocation occurs when the head of the humerus moves partially or fully out of the glenoid causing pain and instability in the shoulder. Dislocations may also cause numbness, weakness or tingling near the injury, such as in your neck or down your arm. Shoulder dislocations are caused by trauma (e.g. in sports, a fall, a car accident, etc.).
Shoulder dislocations can occur in any direction (front, back, or down), but the most common is the anterior (front) dislocation. It can be a very serious injury, especially if it is not able to relocate itself on its own (called spontaneous relocation). In those cases, the patient should seek immediate medical attention to have the shoulder joint put back into place. In other cases, the shoulder muscles need to be specifically strengthened so that they can help to prevent future dislocation.