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Shoulder

Shoulder Dislocation / Instability

The shoulder is a ball-and-socket joint. The ball is the head of the upper arm bone (the humerus), and the socket (the glenoid) is located in the shoulder blade (scapula). Together, the shoulder joint is called the glenohumeral joint.

The shoulder joint is the most mobile joint in the body, allowing a wide range of motion. This mobility is made possible by a complex network of muscles, ligaments, and the joint capsule. However, this inherent mobility also makes the shoulder more susceptible to instability. When the ligaments and joint capsule that provide static stability to the shoulder are stretched, torn, or otherwise damaged, the dynamic stability provided by the muscles and tendons is often insufficient to maintain joint integrity under stress. Consequently, the humeral head may move excessively within or outside its socket, resulting in subluxation (the humeral head is loose and slides around within the socket) or dislocation (the humeral head moves out of the socket).

Shoulder dislocation is the common first-time presentation of shoulder instability. Dislocations occur when the humeral head is forced completely out of the glenoid socket. In a shoulder subluxation, the head of the humerus slips or is partially displaced from its normal position in the glenoid.

Extreme force that impacts the joint can force the arm outward, upward, or backward, causing the shoulder to dislocate. Dislocations can occur from a fall, direct blow to the shoulder, or twisting of the arm and often occur during sports. They may result in rotator cuff tears, labral tears, and even fractures of the shoulder.

  • Severe pain
  • Bruising and swelling
  • Inability to move the joint
  • Muscle spasms
  • Deformity or abnormal appearance of the shoulder
  • Numbness/tingling and weakness

Immediate treatment involves reduction, which involves repositioning the humeral head back into the glenoid socket. This can be performed on the field or in the emergency room. Pain management, immobilization, and rehabilitation exercises follow to restore function and strength.

Recurrent shoulder instability is characterized by the shoulder joint’s inability to maintain the ball in its socket. This occurs as a result of repeated recurrent dislocations or subluxations. This condition can significantly impact an individual’s ability to perform daily activities and maintain an active lifestyle.

Causes of shoulder instability include:

  • Traumatic injuries leading to a repeat dislocation
  • Young patients under the age of 20-25 are much more likely to have a repeat dislocation than older patients.
  • Excessive flexibility or looseness in ligaments that naturally hold the joint together

Treatment aims at restoring stability to the shoulder. This may involve:

  • Physical therapy to strengthen the shoulder muscles, which are dynamic stabilizers of the shoulder
  • Activity modification to avoid movements that could cause the shoulder to dislocate
  • Surgical intervention to repair damaged ligaments and tighten the joint capsule

Shoulder instability requires a comprehensive management approach involving initial acute care, rehabilitation, and, in some cases, surgical intervention to prevent recurrence and ensure the functional integrity of the shoulder joint. Advanced imaging techniques such as MRI can be helpful in assessing the extent of injury and guiding treatment.

When you or a loved one experiences shoulder dislocations and instability, it is important to seek professional care. The UCSF Women’s Sports Medicine Center supports female athletes of all ages and abilities, from the recreational to the elite athlete, with a team of sports medicine and orthopedic specialists. We offer comprehensive care to help our patients recover well and learn how to avoid reinjury to achieve their desired physical activity and performance. Contact us to schedule a consultation to learn more.

References

  • https://orthoinfo.aaos.org/en/diseases–conditions/dislocated-shoulder/
  • Rawal A, Eckers F, Lee OSH, Hochreiter B, Wang KK, Ek ET. Current Evidence Regarding Shoulder Instability in the Paediatric and Adolescent Population. J Clin Med. 2024 Jan 26;13(3):724. doi: 10.3390/jcm13030724. PMID: 38337418; PMCID: PMC10856087.
  • Stokes DJ, McCarthy TP, Frank RM. Physical Therapy for the Treatment of Shoulder Instability. Phys Med Rehabil Clin N Am. 2023 May;34(2):393-408. doi: 10.1016/j.pmr.2022.12.006. Epub 2023 Feb 26. PMID: 37003660.
  • Tokish, John M. MD. Shoulder Instability. Sports Medicine and Arthroscopy Review 28(4):p 121, December 2020. | DOI: 10.1097/JSA.0000000000000295
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