Shoulder instability is a condition in which the upper-end of the humerus (the upper arm bone) slides partially or completely out of the shoulder socket.
Normally, the head of the humerus, moves within the confines of the shoulder socket. Instability occurs when the head slips outside its normal position. The humeral head may move in one or more directions. The disorder is classified by how much this bone moves and by the direction it moves:
- Subluxation—The humeral head moves part way out of the shoulder socket.
- Dislocation—The humeral head moves completely out of the socket.
- Anterior—The humeral head moves toward the front. This is the most common form, which typically occurs in young men. Athletes with great shoulder flexibility are more prone to the disorder. Reinjury is more common in teens and young adults, because they have more elasticity in their shoulder capsule and ligaments. This can lead to later chronic instability.
- Posterior—The humeral head moves toward the back. This is often caused by a severe muscle spasm, such as during an electric shock or seizure
Shoulder instability often results from an initial acute injury producing a dislocation that, even with healing, leads to stretching of the shoulder capsule and ligaments. This type of injury could be due to a fall, a direct hit, or force applied to the outstretched arm. More rarely, shoulder instability develops slowly without any history of previous injury. In some cases, the shoulder may slip out of place at predictable times, such as when lifting a suitcase or even when shaving.
A risk factor is something that increases your chance of getting a disease or condition. Risk factors for shoulder instability include:
Athletic activity, especially:
- Any contact sport
- Swimming, especially backstroke or butterfly
- Congenital collagen disorders, such as:
- Family members with shoulder instability
Symptoms may come on suddenly or develop over time. Symptoms may include:
- Pain in the shoulder area
- Shoulder or arm weakness
- Shoulder may feel loose
- Shoulder may slip out of place
- Numb feeling down the arm
The doctor will ask about your symptoms and medical history, and perform a physical exam. Special attention will be given to your shoulders. Your doctor will determine your range of motion and try to move the humeral head within the socket.
Tests may include:
Therapy will depend on the extent of the injury, the cause, and other factors. Treatment may include:
- Rest—Avoid activities that produce pain or stress the joint.
- Ice—This helps to control pain, especially after exercise.
Medication—Nonsteroidal anti-inflammatory drugs (NSAIDs) may be given to manage pain. These include:
- Ibuprofen (Motrin, Advil)
Rehabilitation—This can last several months and may include:
- Physical therapy to strengthen the muscles that control the shoulder joint, particularly the internal rotators of the shoulder
- Specific exercises for certain sports or job activities
- Learning how to modify activities to prevent reinjury
- Surgery—Many different procedures may be used to correct shoulder instability. The goal is to fix the cause. The doctor may use an arthroscopic
Guidelines to help protect the shoulder from injury include:
- Do regular exercise to strengthen the supporting muscles.
- Use proper athletic training methods.
- Do not increase exercise duration or intensity more than 10% per week.
- Modify activities to prevent excessive external rotation and overhead motions of the shoulder.
American Academy of Family Physicians
American Academy of Orthopaedic Surgeons
Canadian Orthopaedic Association
Canadian Orthopaedic Foundation
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Last reviewed November 2008 by
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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