Not surprisingly, the body's most mobile joint is also the one that is most frequently dislocated. A sudden blow or a fall can cause this condition. When this happens, you usually know. The pain can be severe.

In some individuals, shoulder dislocation continues to happen — creating what is called an "unstable" shoulder.

Shoulder dislocations and separations most frequently happen in younger, athletic individuals. Having had a shoulder dislocation also puts you at higher risk for redislocation. The younger you are when you first dislocate your shoulder, the higher the chance that it will happen again.

View an animation of shoulder dislocation.

The shoulder joint (glenohumeral joint) is made up of a ball and socket joint. The flat bone of the socket has surrounding tissue called the labrum (def.)Labrum The labrum is a thick fibrous rim of tissue surrounding the glenoid or "socket" portion of the shoulder. It deepens the socket to provide more stability for the humeral head or "ball.". The labrum gives it the extra depth it needs to help hold the ball in the socket. Ligaments of the joint capsule provide additional support.

When the ball comes out of the socket during a dislocation, a portion of the labrum is torn or separated from the socket. This is called a Bankart (def.)Bankart Lesion A Bankart lesion is a tear in the labrum, the fibrous tissue that circles the glenoid (shoulder socket). The labrum acts as a "rubber washer" to which the shoulder capsule attaches. Individuals who dislocate their shoulder often tear this "washer" off the socket. tear or SLAP lesion (def.)SLAP Lesion (Superior Labral tear from Anterior to Posterior Lesion) A SLAP lesion is an injury to the labrum, the fibrous rim of tissue surrounding the "socket" portion of the shoulder. SLAP describes how the tendon tears: Superior Labral tear from Anterior to Posterior., with the name depending on the location of the tear. In addition, the capsule may become stretched.

• A dislocated shoulder happens when a strong force or extreme shoulder rotation pulls the "ball" of the upper arm bone out of the socket. About 90% of all shoulder dislocations are this form of injury, called "anterior dislocation" because the top of the bone slips out in front of the shoulder joint.
• If the dislocation is partial, it's called subluxation. The joint is loose and may slide partially out of place. In this case, the labrum may still be attached, but the capsule is stretched out.

There are 2 types of patients with shoulder instability. Treatment depends on which type of dislocation you have:

• Dislocation resulting from injury. When an injury forces the ball out of the socket, treatment to put the ball back into the socket is usually done in an emergency room. If the shoulder dislocates again, surgery may be recommended.
• Dislocation resulting from looseness in ligaments and shoulders. Some shoulder dislocations reoccur without significant injury. Physical therapy to strengthen muscles to help hold the ball in the socket may be useful in these cases. Surgery usually isn't recommended unless therapy has failed after several months.

A separated shoulder occurs where the collarbone (clavicle) and shoulder blade (scapula) meet. It happens when the ligaments that normally hold the collar bone down are torn. The outer end of the collarbone slips out of place. This usually is caused by a severe blow to the shoulder, or by falling on an outstretched hand. The collar bone will stick up and a bump can be seen on top of the shoulder.

Your physician will do a thorough examination to find the source of your pain:

• When your shoulder is dislocated, your arm will look out of position. You will have severe pain, particularly if muscle spasms are present
  
  • In a partial dislocation (subluxation), you may have the sensation that your upper arm bone can slip out of its socket. Your doctor may order an x-ray to confirm the diagnosis and check for fractures.
• A shoulder separation will involve pain and tenderness. Sometimes a bump will appear in the mid top of your shoulder. Your doctor may order an x-ray to confirm the diagnosis and check for fractures. An MRI (def.)MRI (Magnetic Resonance Imaging) MRI is a special diagnostic study that uses strong magnetic fields to visualize bony and soft tissue structures. MRI creates images of bone, muscle, tendons, ligaments and all other soft tissues. may be ordered to make sure there are no other injuries.

For a dislocated shoulder, the doctor will treat the problem by placing the "ball" of the upper arm back in the socket — bringing instant relief. This is called a "reduction." The doctor may suggest additional measures including immobilization, ice packs, and a rehabilitation program of physical therapy to help restore mobility and strengthen the arm. This will help reduce the likelihood of future dislocation.

If you have dislocated your shoulder before, or continue to have problems, your doctor may suggest minimally invasive surgery called arthroscopic surgery or traditional open surgery to correct the problem.

When the problem is a separated shoulder, your doctor may suggest immobilization, ice packs, and a rehabilitation program of physical therapy to help restore mobility and strengthen the arm.

Most shoulder separations heal within a few months without further treatment. However, sometimes the ligaments are too severely torn to keep the clavicle in place. If this is the case, your doctor may suggest surgery.

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Most shoulder separations heal within a few months without further treatment. Younger patients remain at higher lifetime risk for a repeat dislocation and may benefit from surgery to repair torn ligaments and prevent additional dislocations.