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Shoulder Dislocation

Dislocated Shoulder Facts

If your shoulder is wrenched upward and backward, you may dislocate 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 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.

The vast majority of shoulder dislocations (up to 98%) are anterior dislocations (in which the upper arm bone detaches from the shoulder socket and pushes forward). There are four types of anterior shoulder dislocations:

  • Subcoracoid
  • Subglenoid
  • Subclavicular
  • Intrathoracic

Posterior shoulder dislocations, in which the upper arm bone detaches and goes toward the back, are much less common (about 4% of all shoulder dislocations). The rarest type of shoulder dislocation is inferior glenohumeral dislocation (luxatio erecta humeri) and makes up just 1% of all shoulder dislocations.

Picture of Normal Shoulder Joint
Picture of Normal Shoulder Joint
Picture of Shoulder Dislocation
Picture of Shoulder Dislocation
Medically Reviewed by a Doctor on 11/18/2016

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Shoulder Dislocation: A Painful Injury

The shoulders are the most common joint in the body to dislocate. The arm is moved away from the body (abducted) and externally rotated (turning the forearm, palm side up). The joint gives way, and the humeral head, or the ball of the joint, is ripped out of the socket. The structures that hold the shoulder together are torn, including the joint capsule, cartilage, and the ligaments of the rotator cuff.

People with this injury appear in the ER in a fair amount of pain, and pain control is the first priority. The usual sequence of events begins with drugs to help with the pain, a quick exam by the doctor, followed by x-raysto make sure no bones are broken. Then the dislocated shoulder can be reduced; and most people prefer to be aggressively sedated for the procedure.

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Shoulder Dislocation »

Shoulder dislocations may occur from a traumatic injury or from loose capsular ligaments.

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