Dislocated Shoulder: Arm Effects, Symptoms, Causes, and Recovery

What happens to your arm when you dislocate your shoulder?

When your shoulder dislocates, the head of your humerus (upper arm bone) forcibly separates from the glenoid fossa (socket) of your scapula (shoulder blade), leading to immediate and severe pain, visible deformity, and a significant loss of function in the entire arm due to compromised joint integrity, potential nerve damage, and muscle spasm.

Understanding the Shoulder Joint

To grasp the impact of a shoulder dislocation, it's crucial to understand the anatomy of this complex joint. The shoulder is a ball-and-socket joint, specifically the glenohumeral joint, known for its remarkable range of motion but also its inherent instability.

• Humerus: The "ball" is the head of the humerus, your upper arm bone.
• Scapula: The "socket" is the glenoid fossa, a shallow depression on your shoulder blade.
• Glenoid Labrum: A ring of fibrocartilage that deepens the glenoid fossa, providing additional stability.
• Joint Capsule: A fibrous sac enclosing the joint, lined with a synovial membrane.
• Ligaments: Strong, fibrous bands (e.g., glenohumeral ligaments) that reinforce the capsule and connect bones, limiting excessive movement.
• Rotator Cuff Muscles: A group of four muscles (supraspinatus, infraspinatus, teres minor, subscapularis) and their tendons that surround the joint, providing dynamic stability and facilitating rotation and abduction of the arm.

The shoulder's design prioritizes mobility, making it the most frequently dislocated major joint in the body.

The Mechanics of Dislocation

A shoulder dislocation occurs when a significant force displaces the humeral head completely out of the glenoid fossa. This force often involves a combination of abduction (arm moving away from the body) and external rotation, which is a common position for the humerus to be vulnerable.

• Common Causes: Direct trauma (e.g., a fall onto an outstretched arm), sports injuries (e.g., contact sports, overhead throwing activities), or even seizures.
• Types of Dislocation:
  • Anterior Dislocation: The most common type (over 95%), where the humeral head moves forward and typically inferiorly, resting beneath the coracoid process. This often occurs with abduction and external rotation.
  • Posterior Dislocation: Less common, where the humeral head moves backward, often due to direct blows to the front of the shoulder or from electric shock/seizures.
  • Inferior Dislocation (Luxatio Erecta): Rare, where the arm is forced directly overhead, causing the humeral head to dislocate downwards.

Immediate Changes to the Arm

The moment a shoulder dislocates, your arm experiences a cascade of immediate and severe changes:

• Excruciating Pain: Intense, sharp pain is the hallmark symptom, often radiating down the arm. This is due to the tearing of soft tissues, stretching of nerves, and the unnatural position of the bone.
• Visible Deformity: The most striking visual cue is the altered contour of the shoulder. The normal rounded appearance is lost, replaced by a prominent bulge (the humeral head) either in front, behind, or below the joint, and a flattened or "squared-off" appearance where the humeral head should be. The arm may also appear lengthened or shortened, depending on the dislocation direction.
• Loss of Function and Mobility: The arm becomes immediately unusable. Any attempt to move it, even slightly, causes excruciating pain. The individual will typically support the injured arm with their other hand, holding it close to the body in a protective posture. Muscle spasms around the joint further limit movement.
• Nerve Involvement (Neuropraxia/Axonotmesis): The brachial plexus, a network of nerves that supply the entire arm, lies close to the shoulder joint. A dislocation can stretch, compress, or, in severe cases, even tear these nerves.
  • Axillary Nerve: This is the most commonly injured nerve, leading to numbness or tingling over the outer aspect of the shoulder (deltoid region) and weakness in shoulder abduction (lifting the arm away from the body).
  • Other Nerves: Less commonly, the musculocutaneous, radial, ulnar, or median nerves can be affected, leading to sensory deficits or weakness in other parts of the arm, forearm, and hand.
• Vascular Compromise: While less common than nerve injury, a dislocated shoulder can compress or damage nearby blood vessels, particularly the axillary artery. This is a medical emergency, as it can compromise blood flow to the entire arm, leading to pallor, coolness, diminished pulse, and potential tissue damage.

Associated Injuries

The force required to dislocate a shoulder is often sufficient to cause damage to other structures around the joint. These associated injuries can significantly impact recovery and long-term stability:

• Labral Tears:
  • Bankart Lesion: A tear of the anterior inferior glenoid labrum, often occurring when the humeral head dislocates anteriorly and pulls the labrum away from the bone. A bony Bankart involves a fracture of the glenoid rim.
  • SLAP Lesion (Superior Labrum Anterior-Posterior): A tear of the labrum at the top of the glenoid, often extending into the biceps tendon attachment.
• Rotator Cuff Tears: Especially common in older individuals, the forceful displacement can tear one or more of the rotator cuff tendons.
• Humeral Head Fractures:
  • Hill-Sachs Lesion: A compression fracture or indentation on the posterior-superior aspect of the humeral head, caused when it impacts the anterior rim of the glenoid during an anterior dislocation.
• Ligamentous Damage: Stretching or tearing of the glenohumeral ligaments, contributing to joint instability.
• Capsular Damage: Tearing or stretching of the joint capsule.

The Recovery Process and Long-Term Implications

Once a shoulder is dislocated, prompt medical attention is essential for reduction (repositioning the humeral head back into the glenoid fossa). This is typically performed under sedation or anesthesia.

Following reduction, the arm will usually be immobilized in a sling for a period to allow initial healing of the stretched or torn tissues. The duration depends on the individual's age, activity level, and the presence of associated injuries.

Rehabilitation is a critical phase, focusing on:

• Pain and Swelling Management:
• Restoring Range of Motion: Gradually increasing the ability to move the arm.
• Strengthening: Rebuilding the strength of the rotator cuff and periscapular muscles to improve dynamic stability.
• Proprioception: Retraining the joint's sense of position and movement to improve neuromuscular control.

Long-term implications can include:

• Recurrence: The risk of re-dislocation is significantly higher after an initial episode, especially in younger, active individuals. Each subsequent dislocation can cause further damage and increase chronic instability.
• Chronic Instability: Persistent feeling of the shoulder "giving way" or being loose.
• Osteoarthritis: Repeated dislocations and associated cartilage damage can accelerate the development of degenerative joint disease.
• Persistent Nerve Issues: While most nerve injuries resolve over weeks to months, some may result in long-term weakness or numbness.

When to Seek Medical Attention

A dislocated shoulder is a medical emergency. If you suspect a shoulder dislocation, seek immediate professional medical attention. Do not attempt to reduce the shoulder yourself, as this can cause further damage to nerves, blood vessels, or bones. Prompt and proper management is crucial for optimal recovery and minimizing long-term complications.