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The elbow-joint is a ginglymus or hinge joint. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm.
The elbow is the region surrounding the elbow-joint.
The bony prominence at the very tip of the elbow is the olecranon process of the ulna.
Two main movements are possible at the elbow:
* The hinge-like bending and straightening of the elbow (flexion and extension) happens at the articulation ("joint") between the humerus and the ulna.
* The complex action of turning the forearm over (pronation or supination) happens at the articulation between the radius and the ulna (this movement also occurs at the wrist joint).
In the anatomical position (with the forearm supine), the radius and ulna lie parallel to each other. During pronation, the ulna remains fixed, and the radius rolls around it at both the wrist and the elbow joints. In the prone position, the radius and ulna appear crossed.
Most of the force through the elbow joint is transferred between the humerus and the ulna. Very little force is transmitted between the humerus and the radius. (By contrast, at the wrist joint, most of the force is transferred between the radius and the carpus, with the ulna taking very little part in the wrist joint).
 Muscles, arteries, and nerves
The muscles in relation with the joint are:
* in front, the Brachialis
* behind, the Triceps brachii and Anconæus
* laterally, the Supinator, and the common tendon of origin of the Extensor muscles
* medially, the common tendon of origin of the Flexor muscles, and the Flexor carpi ulnaris
The arteries supplying the joint are derived from the anastomosis between the profunda and the superior and inferior ulnar collateral branches of the brachial, with the anterior, posterior, and interosseous recurrent branches of the ulnar, and the recurrent branch of the radial. These vessels form a complete anastomotic network around the joint.
The nerves of the joint are a twig from the ulnar, as it passes between the medial condyle and the olecranon; a filament from the musculocutaneous, and two from the median.