Anatomy & Background


The shoulder was designed for mobility, which also makes it one of the most unstable joints in the body. The shoulder consists of three osseous joints and one articulation. The stability of the shoulder is dependent on the muscles, ligaments, the glenoid labrum and the joint capsule. There are varying degrees of instability as well as various types of instability. The three main types of instabilities are Unidirectional instabilities, multidirectional instabilities, and subluxation.

Unidirectional Instability


The most common of these is unidirectional instability, which occurs when the ligaments or muscles become lax from an acute injury or overuse injury involving repetitive overhead motions. Anterior instability is the most common unidirectional instability.

Multidirectional Instability


Although less common then a Unidirectional instability, multidirectional instabilities are normally caused by repetitive overhead activities. Swimmers, baseball players, and volleyball players tend to be prone to this type of injury. Individuals who have had previous dislocations of the shoulder are also prone to having a multidirectional instability.

Causes


  • Weakness of the rotator cuff and laxity of the glenohumeral ligaments are the most common cause of shoulder instability.
  • General ligamentous laxity may predispose an individual to instability or dislocation.
  • Repetitive strain injuries (RSI) at work, or overuse activities are common in people who participate in sport activities and individuals who have jobs that require performing activities of a repetitive nature, like working on an assembly line.
  • Those participating in activities like swimming or activities characterized by overhead motion like tennis, softball, baseball, volleyball, overhead throwing and other repetitive sport activities may aggravate the shoulder, resulting in shoulder instability.
  • Sudden trauma or accident like a fall on the shoulder or a fall when the arm is placed in an abducted externally rotated position (hand behind head) can also cause a shoulder dislocation.

Symptoms


Instability

  • General tenderness of the shoulder area
  • Discomfort with movement, especially with overhead activities
  • Pain with overhead activities or sleeping on the effected side
  • Feeling that the arm is “dead” after repeated activity
  • A feeling that the shoulder will “go out” when reaching up and behind the head. This is called the Apprehension Sign.

Treating Shoulder Instability


Conservative treatment of shoulder instability is the first line of action. This includes pain medication to reduce inflammation and associated pain. In addition, a regiment of exercises to improve rotator cuff strength and shoulder stability should be initiated. In more severe cases of instability involving the glenoid labrum, surgical intervention may be necessary.

Medicine Intervenes


Procedures that your physician may recommend and perform in addition to physical therapy.

  • Relocation and initial immobilization of the dislocated shoulder
  • REST and ICE
  • The use of NSAIDS (Non Steroidal Anti-Inflammatory Drugs)
  • Steroidal Injections to reduce inflammation
  • Pain medication to reduce the discomfort and allow the patient to perform the recommended exercises
  • Surgery to correct underlying pathology and avoid instability and repeated dislocations. This may include labral repairs or procedures to tighten the shoulder capsule or ligaments.

Prognosis


Most patients recover full function following a course of conservative care of pain management to alleviate pain and reduce swelling and physical therapy to strengthen and stabilize the shoulder. Those with more involved situations such as labral tears, chronic dislocations and/or rotator cuff tears will require surgery to restore full function.