Sidelined by a Dislocated Shoulder
The shoulder is the most mobile and least stable joint in the body. Its
ability to move in many directions makes it prone to dislocation, and in younger
people, sports injuries are a common reason. Throwing or reaching for a ball
puts the shoulder at risk because there is little that stabilizes the shoulder
Shoulder dislocation facts
- The shoulder joints are the most commonly dislocated joints in the body.
- Approximately 25% of shoulder dislocations have associated fractures.
- Closed reduction, without the need for surgery, is the most common initial treatment. Medications may be required for sedation to help facilitate the reduction.
- Immobilization with a
sling is important to decrease the risk of a repeat dislocation. First dislocations are immobilized in an external rotation position. Recurrent dislocations may be immobilized in a regular sling.
follow-up is important to decide when to begin allowing shoulder motion.
time of immobilization varies, and balance needs to exist between shoulder
stability and loss of motion and function from prolonged immobilization.
- Uncomplicated rehabilitation and healing will allow return to normal function in
What is dislocation of the shoulder? What causes a shoulder dislocation?
The shoulder joint is the most mobile joint in the body and allows the arm to
move in many directions. This ability to move makes the joint inherently
unstable and also makes the shoulder the most often dislocated joint in the
In the shoulder joint, the head of the humerus (upper arm bone) sits in the glenoid fossa, an extension of the scapula, or shoulder blade. Because the glenoid fossa (fossa = shallow depression) is so shallow, other structures within and surrounding the shoulder joint are needed to maintain its stability. Within the joint, the labrum (a fibrous ring of cartilage) extends from the glenoid fossa and provides a deeper receptacle for the humeral head. The capsule tissue that surrounds the joint also helps maintain stability. The rotator cuff muscles and the tendons that move the shoulder provide a significant amount of protection for the shoulder joint.
Dislocations of the shoulder occur when the head of the humerus is forcibly removed from its socket in the glenoid fossa. It's possible to dislocate the shoulder
in many different directions, and a dislocated shoulder is described by the location where the humeral head ends up after it has been dislocated. Ninety percent or more of shoulder dislocations are anterior dislocations, meaning that the humeral head has been moved to a position in front of the joint. Posterior dislocations are those in which the humeral head has moved backward toward the shoulder blade. Other rare types of dislocations include luxatio erecta, an inferior dislocation below the joint, and intrathoracic, in which the humeral head gets stuck between the ribs.
Picture of the shoulder joint
Dislocations in younger people tend to arise from trauma and are often
associated with sports or falls. Older patients are prone to dislocations
because of gradual weakening of the ligaments and cartilage that supports the shoulder. Even in these cases, however, there still needs to be some force applied to the shoulder joint to make it dislocate.
Anterior dislocations often occur when the shoulder is in a vulnerable
position. A common example is when the arm is held over the head with the elbow
bent, and a force is applied that pushes the elbow backward and levers the
humeral head out of the glenoid fossa. This scenario can occur with throwing a
ball or hitting a volleyball. Anterior dislocations also occur during falls on
an outstretched hand. An anterior dislocation involves external rotation of the
shoulder; that is, the shoulder rotates away from the body.
Posterior dislocations are uncommon and are often associated with specific
injuries like lightning strikes, electrical injuries, and seizures. On occasion, this type of dislocation can occur with minimal injury in the elderly, and because X-rays may not easily show a posterior dislocation, the diagnosis is often missed should the patient present for evaluation of shoulder pain.
Medically Reviewed by a Doctor on 4/30/2015