If your shoulder is wrenched upward and backward, you may have dislocated it out of its socket. This condition is both painful and incapacitating. The force required is often that of a fall or a collision with another person or object (both of which can occur during many sports). Most shoulder dislocations happen at the lower front of the shoulder, because of the particular anatomy of the shoulder joint. The bones of the shoulder are the socket of the shoulder blade (scapula) and the ball at the upper end of the arm bone (humerus). The socket on the shoulder blade is fairly shallow, but a lip or rim of cartilage (the glenoid labrum) makes it deeper. The joint is supported on all sides by ligaments called the joint capsule, and the whole thing is covered by the rotator cuff. The rotator cuff is made up of four tendons attached to muscles that start on the scapula and end on the upper humerus. They reinforce the shoulder joint from above, in front, and in back, which makes the weakest point in the rotator cuff in the lower front.
Subluxation refers to a partial dislocation. A subluxation occurs when the two joint (articular) surfaces have lost their usual contact. A 50% subluxation means the normally opposing articular surfaces have lost half their usual contact and the joint is partially dislocated. A 100% subluxation means the articular surfaces have lost all of their contact. A dislocation is the same as a 100% subluxation.
Most Common Causes of Dislocated Shoulder:
- Traumatic Shoulder Dislocation – High speed or traumatic shoulder dislocation occurs when your shoulder is in a vulnerable position and is popped out at speed. Commonly this is with your arm out to the side. This injury description is common when dislocating in a football tackle or during a fall.
- Repetitive Shoulder Ligament Overstrain Occasionally, people with looser ligaments in their shoulders can dislocate their shoulders with relative ease. This increased passive shoulder instability is sometimes just your normal anatomy. Sometimes, it is the result of repetitive overstretching of the shoulder joint. Some sports such as swimming, tennis, throwing sports (cricket, baseball etc.) and volleyball that require repetitive overhead motion can overstretch your shoulder ligaments and joint capsule. Looser shoulder ligaments make it harder for your shoulder’s rotator cuff muscles to maintain your shoulder stability. If you have an unstable shoulder, the best thing that you can do to prevent or help rehabilitate your shoulder dislocation is to undertake a specific shoulder rotator cuff strengthening program. Please ask your physical therapist for their professional advice.
- Multi-Directional Instability – In a small number of patients, your shoulder is unstable in multiple directions due to your genetic disposition. In these patients, the shoulder may feel loose or dislocate repeatedly in multiple directions. This is called multi-directional instability. These patients have naturally loose ligaments throughout the body and may be “double-jointed” or hypermobile. Due to their genetically elastic collagen fibers in their ligaments, these patients typically do not respond with much success to surgical stabilization. They are best managed with a thorough shoulder stabilization strengthening program. Please ask your physical therapist for their professional advice.
Both acute and repeated shoulder dislocations are normally treated initially with non-operative rehabilitation guided by your physical therapist. Stabilization surgery may be considered should your exercise-based treatment fail.