The elbow is a stable joint relying primarily on bony anatomy rather than ligaments; the elbow joint is where the bones of the forearm, the radius and ulna, meet the upper arm, or humerus. Fractures are frequently seen with this injury due to the force required to dislocate such a stable joint.

Elbow dislocations fall under two main classifications: simple or complex. Simple elbow dislocations, involving primarily the bones of the elbow, are defined by the direction the forearm bones go relative to the humerus as listed below. When fractures and/or neuromuscular injuries accompany elbow dislocations, they are considered complex.

Simple elbow dislocation classifications:
1) Posterior – the radius and ulna go behind the humerus (most common);
2) Anterior – the radius and ulna go in front of the humerus;
3)  Medial – the radius and ulna go inward relative to the humerus;
4) Lateral – the radius and ulna go outward relative to the humerus;
5) Divergent – the radius and ulna go in opposite directions relative to the humerus (rare).

Most injuries of this nature are sports related but can also occur during work related or automobile accidents. The injury is often described as a fall on the wrist with the elbow locked out, or extended.

Further Reading:

American Academy of Orthopaedic Surgeons: Elbow Dislocations and Fracture-Dislocations