Elbow Dislocation: Causes, Mechanisms, Types, and What to Do

What causes a dislocated elbow?

An elbow dislocation occurs when the bones of the forearm (radius and ulna) are forced out of their normal alignment with the upper arm bone (humerus), most commonly due to significant trauma, such as a fall onto an outstretched arm or a direct impact.

Understanding Elbow Anatomy and Stability

The elbow is a complex hinge joint formed by the articulation of three bones: the humerus (upper arm bone) and the radius and ulna (forearm bones). Its stability is primarily provided by:

• Bony Congruity: The trochlea of the humerus fits snugly into the trochlear notch of the ulna, forming a strong hinge (humeroulnar joint). The capitellum of the humerus articulates with the head of the radius (humeroradial joint).
• Ligamentous Support:
  • Medial Collateral Ligament (UCL): Provides primary valgus (inward) stability.
  • Lateral Collateral Ligament (LCL) Complex: Provides primary varus (outward) stability and posterolateral rotatory stability. This complex includes the radial collateral ligament, lateral ulnar collateral ligament, accessory collateral ligament, and annular ligament.
• Muscular Support: Surrounding muscles and their tendons, while not primary stabilizers, contribute to dynamic stability.

A dislocated elbow implies a disruption of these stabilizing structures, leading to the separation of the joint surfaces.

Primary Mechanisms of Elbow Dislocation

The vast majority of elbow dislocations are caused by high-energy trauma that overwhelms the joint's inherent stability. The most common mechanisms include:

• Fall Onto an Outstretched Hand (FOOSH): This is the predominant cause. When a person falls and attempts to break their fall by extending an arm, the force travels up the forearm to the elbow. If the arm is slightly abducted (away from the body) and externally rotated, and the elbow is in slight flexion, the forces can drive the ulna and radius posteriorly, tearing the stabilizing ligaments.
• Direct Trauma: A direct blow to the elbow, often seen in contact sports (e.g., football, rugby, wrestling) or motor vehicle accidents, can force the bones out of alignment. The direction of the force dictates the type of dislocation (e.g., anterior, posterior, or divergent).
• Hyperextension Injuries: While less common as a sole mechanism for complete dislocation, a severe hyperextension injury can cause the olecranon process of the ulna to lever against the humerus, tearing the anterior capsule and potentially leading to dislocation, often posteriorly.
• Sports-Related Injuries: Activities involving falls, impacts, or repetitive stress that can lead to acute traumatic events are common culprits. Examples include:
  • Gymnastics (e.g., falls from bars)
  • Wrestling and martial arts (e.g., arm bars, takedowns)
  • Football, basketball, and other contact sports
  • Skiing and snowboarding (falls)
• Congenital Ligamentous Laxity: Individuals with generalized joint hypermobility (e.g., Ehlers-Danlos syndrome or benign joint hypermobility syndrome) may have inherently looser ligaments, making them more susceptible to dislocations, even with less significant trauma.

Types of Elbow Dislocations

While the causes are similar, the direction of displacement classifies the dislocation:

• Posterior Dislocation: This is the most common type, accounting for over 90% of elbow dislocations. The forearm bones displace backward relative to the humerus. This often occurs with a FOOSH injury where the arm is slightly abducted and pronated.
• Anterior Dislocation: Much rarer, occurring when the forearm bones displace forward. This typically requires a direct blow to the posterior aspect of the elbow or an anterior directed force on a flexed elbow.
• Divergent Dislocation: Extremely rare, where the radius and ulna separate from each other in addition to dislocating from the humerus.
• Simple vs. Complex Dislocation:
  • Simple Dislocation: Involves only the dislocation of the joint without an associated bone fracture. Ligamentous damage is always present.
  • Complex Dislocation: Involves the dislocation along with one or more fractures of the bones forming the elbow joint (humerus, radius, or ulna). These are generally more severe, require surgical intervention more frequently, and have a longer recovery time.

Risk Factors for Elbow Dislocation

While acute trauma is the direct cause, certain factors can increase an individual's susceptibility:

• Participation in High-Impact Sports: Activities with a high risk of falls or direct contact.
• Previous Elbow Dislocation: Once an elbow has been dislocated, the ligaments are stretched or torn, leading to residual laxity and increasing the risk of re-dislocation.
• Ligamentous Laxity: As mentioned, inherent joint hypermobility can predispose individuals.
• Age: Children and adolescents are particularly susceptible due to their active lifestyles and developing musculoskeletal systems. However, adults engaged in sports or high-risk occupations are also at significant risk.

Recognizing a Dislocated Elbow

A dislocated elbow is an orthopedic emergency. Key signs and symptoms include:

• Severe Pain: Intense pain that makes any movement excruciating.
• Obvious Deformity: The elbow joint will appear visibly deformed, often with a prominent olecranon (the bony tip of the elbow) posteriorly.
• Significant Swelling and Bruising: Rapid onset due to tissue damage and internal bleeding.
• Inability to Move the Arm: The arm is often held in a fixed, slightly flexed position, and any attempt at movement is impossible.
• Numbness or Tingling: May indicate nerve compression or damage (median, ulnar, or radial nerves).
• Absent Pulse: In rare but severe cases, vascular compromise can occur, requiring immediate medical attention.

Immediate Action and Professional Care

If an elbow dislocation is suspected, it is crucial to:

• Do NOT Attempt to Reduce the Dislocation: Trying to put the joint back into place without proper medical training can cause further damage to nerves, blood vessels, or surrounding tissues.
• Immobilize the Arm: Gently support the arm in the position it is found using a sling or improvised splint.
• Seek Immediate Medical Attention: Transport the individual to an emergency room or orthopedic specialist without delay.

Professional medical care will involve imaging (X-rays) to confirm the diagnosis and rule out fractures, followed by a controlled reduction of the dislocation (often under sedation), and subsequent rehabilitation to restore function and stability.