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the complex movable articulation of the human upper arm and forearm, formed by the junction of the humeral, ulnar, and radial bones.
The elbow joint actually consists of three articulations—humeroulnar, humeroradial, and proximal (superior) radioulnar—which have a single joint cavity and capsule. The anatomical characteristics of the articulating bone surfaces determine the nature of the movements in the joint. The combination of hinge (humeroulnar), ball-and-socket (humeroradial), and rotary (proximal radioulnar) articulations allows flexion of the ulna and extension of the forearm and rotation of the radius and the hand around a vertical axis (that is, movement of the hand inward and outward). The range of movements in the elbow joint is about 140°. The diseases most commonly affecting the elbow joint are ankylosis, bursitis, and dislocation.