Shoulder Joint: Subluxation, Dislocation, Causes, Symptoms, and Treatment

What is Subluxation and Dislocation of Shoulder Joint?

Shoulder subluxation and dislocation represent a spectrum of injuries where the head of the humerus (upper arm bone) partially or completely separates from the glenoid fossa (shoulder socket), primarily affecting the stability of the highly mobile glenohumeral joint.

The Shoulder Joint: A Marvel of Mobility and Vulnerability

The shoulder, or glenohumeral joint, is the most mobile joint in the human body, allowing for a vast range of motion in multiple planes. This impressive mobility, however, comes at the cost of inherent stability. It is a ball-and-socket joint where the large humeral head articulates with the relatively shallow glenoid fossa of the scapula. Stability is primarily provided by a complex interplay of static stabilizers (the joint capsule, glenoid labrum, and ligaments) and dynamic stabilizers (the rotator cuff muscles and other periarticular musculature). When these stabilizing structures are compromised, the joint becomes susceptible to instability events like subluxation and dislocation.

Understanding Shoulder Dislocation

A shoulder dislocation occurs when the head of the humerus completely separates from the glenoid fossa. This is a significant traumatic event that results in the humeral head resting outside the joint capsule.

• Definition: Complete displacement of the humeral head from the glenoid cavity. The joint surfaces are no longer in contact.
• Mechanism/Causes: Most commonly caused by a direct blow to the shoulder, a fall onto an outstretched arm (FOOSH), or a forceful external rotation and abduction of the arm. High-impact sports (e.g., football, rugby, wrestling) and motor vehicle accidents are frequent culprits.
• Types:
  • Anterior Dislocation: The most common type (over 95%), where the humeral head moves forward and typically inferiorly, often resting under the coracoid process.
  • Posterior Dislocation: Less common, often resulting from direct trauma to the front of the shoulder or from seizures/electrocution where strong internal rotation forces are generated.
  • Inferior Dislocation (Luxatio Erecta): Rare, where the arm is forced into hyperabduction, causing the humeral head to displace inferiorly.
• Symptoms:
  • Severe, immediate pain.
  • Visible deformity of the shoulder: The shoulder may appear "squared off" or flattened, with a prominent acromion.
  • Inability to move the arm.
  • Arm held in an abnormal position: Often slightly abducted and externally rotated for anterior dislocations.
  • Numbness or tingling: May occur if nerves (e.g., axillary nerve) are compressed or stretched.
  • Swelling and bruising.
• Immediate Action: A dislocated shoulder is a medical emergency. Do not attempt to reduce the shoulder yourself. Seek immediate medical attention. Keep the arm as still as possible, ideally in a sling or supported position.

Understanding Shoulder Subluxation

A shoulder subluxation is a less severe form of instability compared to a dislocation. It involves a partial or incomplete separation of the humeral head from the glenoid fossa, where the humeral head momentarily slips out of the socket but then spontaneously returns to its normal position.

• Definition: Partial or incomplete displacement of the humeral head from the glenoid cavity, followed by spontaneous reduction. The joint surfaces lose some contact but do not fully separate.
• Mechanism/Causes: Often similar to dislocations but with less force involved. It can occur during overhead activities, throwing motions, or less severe falls. It's common in individuals with underlying shoulder instability, such as those with ligamentous laxity or previous shoulder injuries.
• Symptoms:
  • Sudden, sharp pain: Often transient, as the joint reduces quickly.
  • Sensation of the shoulder "slipping out" or "giving way."
  • Temporary weakness or instability.
  • Apprehension: A feeling that the shoulder might slip out again, especially in certain positions (e.g., arm abducted and externally rotated).
  • Mild swelling or tenderness after the event.
  • No obvious visible deformity after reduction.
• Recognition: Because the joint often reduces on its own, subluxation can sometimes be dismissed as a "tweak" or "strain." However, the sensation of the joint moving out of place is a key differentiator. Recurrent subluxations indicate underlying instability that requires assessment.

Key Differences Between Subluxation and Dislocation

While both involve displacement of the humeral head, their severity and implications differ significantly:

• Degree of Separation:
  • Dislocation: Complete loss of contact between articular surfaces.
  • Subluxation: Partial or temporary loss of contact, with spontaneous return.
• Symptoms Severity:
  • Dislocation: Intense, persistent pain; obvious deformity; complete loss of function.
  • Subluxation: Transient pain; sensation of "slipping"; no sustained deformity; temporary functional impairment.
• Medical Intervention:
  • Dislocation: Requires immediate medical reduction (repositioning) by a professional.
  • Subluxation: Often self-reduces, but medical evaluation is crucial to assess underlying instability and prevent recurrence.
• Ligamentous Damage: Dislocation almost always involves significant stretching or tearing of the joint capsule and ligaments (e.g., Bankart lesion of the labrum). Subluxation can also cause damage, but often to a lesser extent, though repeated subluxations can lead to cumulative damage similar to a dislocation.
• Recovery: Dislocation typically requires a longer period of immobilization and rehabilitation. Subluxation recovery may be quicker initially but requires diligent rehabilitation to address chronic instability.

Common Causes and Risk Factors

Several factors contribute to the risk of both subluxation and dislocation:

• Traumatic Injury: Falls onto an outstretched arm, direct blows to the shoulder, sports injuries (e.g., contact sports, overhead throwing sports, gymnastics).
• Ligamentous Laxity: Individuals with naturally loose ligaments (hypermobility syndrome) may be more prone to instability.
• Muscle Imbalance or Weakness: Weakness in the rotator cuff muscles, periscapular muscles, or imbalances between internal and external rotators can compromise dynamic stability.
• Previous Injury: A history of a prior shoulder dislocation or subluxation significantly increases the risk of recurrence due to stretched or torn ligaments and capsular tissue.
• Anatomical Factors: A shallow glenoid fossa or a hypoplastic (underdeveloped) anterior glenoid rim can predispose to instability.

Diagnosis and Medical Intervention

Accurate diagnosis is crucial for appropriate management:

• Physical Examination: A healthcare professional will assess pain, range of motion, stability, and check for nerve or blood vessel damage. Specific tests (e.g., apprehension test, relocation test) can help identify instability.
• Imaging:
  • X-rays: Essential to confirm a dislocation, determine its direction, and rule out fractures of the humerus or glenoid.
  • MRI (Magnetic Resonance Imaging): Often used after reduction to assess soft tissue damage, such as labral tears (e.g., Bankart lesion), rotator cuff tears, or capsular injuries.
• Reduction (for Dislocation): Once a dislocation is confirmed, the humeral head must be gently and skillfully repositioned back into the glenoid fossa by a trained medical professional. This procedure, called reduction, often requires pain medication and/or sedation.

Rehabilitation and Prevention

Rehabilitation is critical for restoring function and preventing recurrence after both subluxation and dislocation.

• Initial Management (Acute Phase):
  • RICE Protocol: Rest, Ice, Compression (if applicable), Elevation.
  • Immobilization: A sling is typically used for a period (e.g., 1-3 weeks for dislocation) to allow initial healing, though prolonged immobilization can lead to stiffness.
  • Pain Management: NSAIDs and/or other pain relievers.
• Physical Therapy: This is the cornerstone of recovery.
  • Restoration of Range of Motion: Gentle, progressive exercises to regain mobility.
  • Strengthening: Focus on the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis), deltoid, and periscapular muscles (e.g., rhomboids, serratus anterior, trapezius) to enhance dynamic stability.
  • Proprioception Training: Exercises that improve the body's sense of joint position and movement, essential for neuromuscular control and preventing re-injury. Examples include balance exercises on unstable surfaces or perturbations to the arm.
  • Sport-Specific or Activity-Specific Training: Gradually reintroducing movements relevant to the individual's activities or sport.
• Surgical Considerations: Surgery may be recommended for recurrent dislocations, significant labral tears (e.g., Bankart lesion), bone loss from the glenoid (bony Bankart) or humeral head (Hill-Sachs lesion), or if conservative management fails. The goal is to repair damaged structures and restore stability.
• Preventative Strategies:
  • Proper Technique: In sports and daily activities, ensure correct biomechanics, especially during overhead movements.
  • Strength and Conditioning: Maintain balanced strength in the shoulder complex and surrounding musculature.
  • Warm-up and Cool-down: Prepare muscles for activity and aid recovery.
  • Protective Gear: Use appropriate padding or bracing in high-risk sports.
  • Listen to Your Body: Avoid pushing through pain or a feeling of instability.

When to Seek Medical Attention

Always seek immediate medical attention for a suspected shoulder dislocation. For subluxation, even if it self-reduces, it is highly advisable to consult a healthcare professional (orthopedic surgeon, sports medicine physician, or physical therapist) to:

• Confirm the diagnosis and rule out more serious injuries.
• Assess the extent of underlying ligamentous or capsular damage.
• Develop a comprehensive rehabilitation plan to address chronic instability and prevent future episodes.
• Discuss potential surgical options if conservative treatment is insufficient or if there are significant structural injuries.

Understanding the distinctions and implications of shoulder subluxation and dislocation is crucial for effective management and long-term joint health. Through proper diagnosis, timely intervention, and dedicated rehabilitation, individuals can often return to their desired levels of activity.