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 partially 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.
• Inferior—The humeral head drops downward.
• Multidirectional—The humeral head moves toward difference places.

Causes

Shoulder instability often results from injury.

Risk Factors

Factors that may increase your chance of shoulder instability include:

• Trauma, such as a fall with an outstretched arm or a direct blow to the shoulder
• 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:
  • Marfan syndrome—a connective tissue condition
  • Ehlers-Danlos syndrome—a condition marked by loose joints
• Family members with shoulder instability

Symptoms

Symptoms may come on suddenly or develop over time. Shoulder instability may cause:

• 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.

Imaging tests evaluate your shoulder and surrounding structures. These may include:

• X-rays
• MRI scan
• CT scan

Arthroscopy is done with an instrument with a long tube and miniature camera on the end. Repairs or corrections can be made while the doctor evaluates the shoulder joint.

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 and inflammation, 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 3 to 6 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

Ortho Info—American Academy of Orthopaedic Surgeons http://orthoinfo.org

Canadian Orthopaedic Foundation http://www.canorth.org

Desmeules F, Barry J, Roy JS, Vendittoli PA, Rouleau DM. Surgical interventions for post-traumatic anterior shoulder instability in adults. Cochrane Database of Systematic Reviews 2014;(5):CD011092.

Dumont GD, Russell RD, et al. Anterior shoulder instability: a review of pathoanatomy, diagnosis, and treatment. Curr Rev Musculoskelet Med. 2011 Aug 2.

Gaskill TR, Taylor DC, et al. J Am Acad Orthop Surg. 2011 Dec 19(12):758-767.

Luime JJ, Verhagen AP, et al. Does this patient have an instability of the shoulder or a labrum lesion? JAMA. 2004;292:1989-1999.

Mahaffey BL. Smith PA. Shoulder instability in young athletes. Am Fam Physician. 1999;59:2773.

Nassiri N, Eliasberg C, Jones KJ, McAllister DR, Petrigliano FA. Shoulder instability in the overhead athlete: A systematic review comparing arthroscopic and open stabilization procedures. 2015;3(2):suppl2325967115S00154.

Owens BD, Campbell SE, Cameron KL. Risk factors for anterior glenohumeral instability. Am J Sports Med. 2014;42(11):2591-2596.

Provencher MT, Frank RM, et al. The Hill-Sachs lesion: diagnosis, classification, and management. J Am Acad Orthop Surg. 2012 Apr;20(4):242-252.

Recurrent subluxation of shoulder. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed
Updated August 21, 2014. Accessed September 16, 2015.

van Tongel A, Karelse A, et al. Posterior shoulder instability: current concepts review. Knee Surg Sports Traumatol Arthrosc. 2011 Sep;19(9):1547-1553.

von der Heyde RL. Occupational therapy interventions for shoulder conditions: a systematic review. Am J Occup Ther. 2011 Jan-Feb;65(1):16-23.

Wilk KE and Macrina LC. Nonoperative and postoperative rehabilitation for glenohumeral instability. Clin Sports Med. 2013; 32:865-914.

Wolf JM, Cameron KL, et al. Impact of joint laxity and hypermobility on the musculoskeletal system. J Am Acad Orthop Surg. 2011 Aug;19(8):463-471.