Definition

Shoulder instability occurs when the upper-end of the arm bone, known as the humerus, slides partially or completely out of the shoulder socket.

The disorder is classified by how much the humerus moves and the direction of the movement:

  • 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.
  • Posterior—The humeral head moves toward the back.
  • Multidirectional

Shoulder Instability

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Causes

Shoulder instability often results from injury.

Risk Factors

Factors that increase the risk of shoulder instability include:

  • Previous shoulder dislocation
  • Athletic activity, especially:
    • Baseball—pitching
    • Football—tackling
    • Tennis
    • Gymnastics
    • Weight-lifting
    • Any collision or contact sport
    • Volleyball
    • Swimming, especially backstroke or butterfly
  • Congenital collagen disorders, such as:
  • Family members with shoulder instability

Symptoms

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

Diagnosis

You will be asked about your symptoms and medical history. A physical exam will be done. 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.

Your shoulder may need to be viewed. This can be done with:

Treatment

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), such as aspirin or ibuprofen, may be given to manage pain.
  • 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. An arthroscopic or an open technique may be used. After surgery, the arm is kept from moving for three to six weeks, depending on the procedure.

Prevention

Guidelines to help protect the shoulder from injury include:

  • Doing regular exercises to strengthen the supporting muscles
  • Using proper athletic training methods
  • Increasing the duration or intensity of your exercises gradually
  • Modifying activities to prevent excessive external rotation and overhead motions of the shoulder