Recurrent Shoulder Dislocation: Causes, Symptoms, Diagnosis, and Treatment

Why does my arm keep popping out of place?

Recurrent arm "popping out" – medically termed shoulder dislocation or subluxation – is primarily due to underlying instability of the glenohumeral (shoulder) joint, often stemming from previous injury, anatomical factors, or generalized ligamentous laxity.

Understanding Shoulder Instability

The shoulder is the most mobile joint in the human body, a characteristic that unfortunately comes at the cost of stability. It's a ball-and-socket joint where the head of the humerus (arm bone) articulates with the shallow glenoid fossa of the scapula (shoulder blade). This inherent design, prioritizing range of motion over stability, relies heavily on soft tissue structures for support:

• Glenoid Labrum: A fibrous rim of cartilage that deepens the glenoid socket, providing a more stable seat for the humeral head.
• Joint Capsule: A fibrous sac enclosing the joint, reinforced by ligaments.
• Glenohumeral Ligaments: Strong bands of connective tissue that connect the humerus to the glenoid, limiting excessive motion.
• Rotator Cuff Muscles: A group of four muscles (supraspinatus, infraspinatus, teres minor, subscapularis) and their tendons that surround the shoulder joint, providing dynamic stability by keeping the humeral head centered in the glenoid during movement.

When your arm "pops out," it means the humeral head has partially (subluxation) or completely (dislocation) come out of the glenoid socket. If this happens repeatedly, it indicates a state of shoulder instability.

Common Causes of Recurrent Shoulder Dislocation/Subluxation

Recurrent instability is almost always a consequence of an initial event or underlying predisposition that compromised the integrity of the shoulder's stabilizing structures.

• Prior Traumatic Dislocation: This is the most common cause. An initial forceful dislocation often damages the soft tissues, making subsequent dislocations more likely.
  • Bankart Lesion: A tear of the anterior (front) glenoid labrum, often with detachment from the bone, occurring when the humeral head dislocates forward. This is a primary culprit for recurrent anterior instability.
  • Capsular or Ligamentous Damage: The joint capsule and glenohumeral ligaments can be stretched, torn, or avulsed (pulled off the bone), leading to chronic laxity.
• Ligamentous Laxity or Generalized Hypermobility: Some individuals naturally have more elastic connective tissues, making their joints inherently more flexible and less stable. Conditions like Ehlers-Danlos syndrome or generalized joint hypermobility can predispose individuals to recurrent dislocations even with minimal trauma.
• Glenoid Bone Loss: With repeated dislocations, the edge of the glenoid bone can erode or fracture, creating a smaller, less effective socket. This "bony Bankart" lesion significantly reduces stability.
• Hill-Sachs Lesion: A compression fracture or indentation on the posterolateral (back and outer) aspect of the humeral head. This occurs when the humeral head impacts the anterior glenoid rim during a dislocation, and it can contribute to subsequent instability by providing a "catch" point.
• Muscle Imbalances or Weakness: Weakness or dysfunction in the rotator cuff muscles or scapular (shoulder blade) stabilizing muscles can compromise dynamic stability, allowing the humeral head to move excessively within the socket.
• Repetitive Overhead Activities: Certain sports (e.g., throwing, swimming, volleyball) can, over time, stretch the shoulder capsule and ligaments, especially if not balanced with adequate strength training for dynamic stabilizers.

Symptoms and Diagnosis

If your arm repeatedly "pops out," you're likely experiencing:

• Pain: Often sharp during the event, followed by a dull ache.
• Apprehension: A feeling that your shoulder might "give way" or pop out again, especially when moving your arm into certain positions (e.g., abduction and external rotation).
• Clicking, Clunking, or Grinding Sensations: These may occur during movement.
• Weakness or Instability: A general feeling of looseness or decreased strength in the affected arm.

Accurate diagnosis requires a thorough medical evaluation by a physician or orthopedic specialist. This typically involves:

• Detailed Medical History: Discussing the circumstances of the initial injury, frequency of "popping," and specific positions that trigger instability.
• Physical Examination: Assessing range of motion, strength, and performing specific stability tests (e.g., apprehension test, sulcus sign) to evaluate ligamentous integrity and joint laxity.
• Imaging Studies:
  • X-rays: To assess for bony abnormalities like glenoid bone loss, Hill-Sachs lesions, or fractures.
  • MRI (Magnetic Resonance Imaging): Often with contrast (MR arthrogram) to visualize soft tissue damage, including labral tears (Bankart lesions), capsular tears, and rotator cuff pathology.

Management and Treatment Approaches

Treatment for recurrent shoulder instability aims to restore stability and function while minimizing the risk of future dislocations. The approach depends on the underlying cause, the degree of instability, and the patient's activity level.

Conservative Management

For mild instability, first-time dislocations without significant structural damage, or in individuals who are not surgical candidates, conservative treatment may be pursued:

• Rest and Immobilization: Initially, a sling may be used to allow acute inflammation to subside and tissues to begin healing.
• Physical Therapy: A cornerstone of conservative management. A structured rehabilitation program focuses on:
  • Strengthening: Rotator cuff muscles and periscapular muscles (e.g., serratus anterior, rhomboids, trapezius) to enhance dynamic stability.
  • Proprioception and Neuromuscular Control: Retraining the brain and muscles to better sense joint position and react appropriately to stabilize the shoulder.
  • Range of Motion: Gradually restoring full, pain-free movement.
  • Activity Modification: Learning to avoid positions or activities that provoke instability.

Surgical Intervention

Surgery is often recommended for individuals with recurrent dislocations, significant anatomical damage (e.g., large Bankart lesion, considerable bone loss), or those whose lifestyle demands a high level of shoulder stability (e.g., athletes).

• Arthroscopic Bankart Repair: The most common procedure for anterior instability. Performed minimally invasively through small incisions, the torn labrum and stretched capsule are reattached to the glenoid bone using small anchors.
• Latarjet Procedure (Coracoid Transfer): A more involved open surgical procedure often used when there is significant glenoid bone loss. A piece of bone (the coracoid process) with its attached muscles is transferred to the front of the glenoid, providing a bony block and muscle sling to prevent further dislocation.
• Remplissage: An arthroscopic procedure sometimes performed in conjunction with a Bankart repair to address a Hill-Sachs lesion, filling the defect to prevent engagement with the glenoid rim.

Post-surgical rehabilitation is critical for successful outcomes, typically involving a period of immobilization followed by a progressive physical therapy program over several months to regain strength, mobility, and function.

Prevention and Long-Term Considerations

While not all dislocations are preventable, especially those due to significant trauma, understanding the risk factors and taking proactive steps can reduce the likelihood of recurrence:

• Consistent Strength Training: Focus on developing balanced strength in the rotator cuff and scapular stabilizing muscles. Exercises like external rotations, internal rotations, band pull-aparts, and rows are beneficial.
• Proper Technique: In sports and weight training, ensure correct form to avoid placing undue stress on the shoulder joint.
• Awareness of Hypermobility: If you have generalized joint hypermobility, be extra vigilant about shoulder stability exercises and avoid extreme ranges of motion that could lead to subluxation.
• Adherence to Rehabilitation: If you've had a dislocation or surgery, completing your entire physical therapy program is paramount to prevent recurrence.
• Listen to Your Body: Do not ignore persistent shoulder pain or feelings of instability. Early intervention can prevent more severe issues.

Recurrent shoulder instability is a complex issue requiring a comprehensive approach. If your arm continues to "pop out," it is essential to consult with an orthopedic specialist or sports medicine physician for an accurate diagnosis and a tailored treatment plan.