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The elbow joint not only allows the arm to flex but also permits the forearm to rotate inwards and outwards (pronation and supination). Good elbow function is essential for everyday activities. Elbow injuries often occur during throwing or falling, and may result in serious complications owing to the proximity to the joint of major blood vessels and nerves.

Functional anatomy

The stability of the elbow is provided by the collateral ligaments and the fibrous capsules, as well as by the bones and their articulations, and the muscles and tendons. The medial ulnar ligament is well
developed and forms three distinct bands: the anterior oblique ligament; a small, transverse, nonfunctional ligament; and the posterior oblique ligament. The anterior oblique ligament is very strong: it is taut through the entire arc of elbow flexion and is the primary constraint of valgus stress of the elbow. The posterior oblique ligament is taut in flexion and lax in extension and does not have a primary role in elbow stability. The lateral collateral ligament stabilizes for varus stress.

The anconeus muscle appears to provide lateral support, as do the forearm extensor muscles. The extensors carpi radialis brevis and longus, digitorum communis, digiti minimi and carporadialis originate at
the lateral epicondyle and are mainly wrist and finger extensors. The three primary flexor muscles of the elbow are the biceps brachii, the brachioradialis, and the brachialis. The most important pronator muscles of the elbow are the pronator teres and the pronator quadratus. The triceps is the only effective extensor of the

The radial nerve runs anterior lateral of the elbow and divides into the posterior interosseous nerve and the lateral cutaneous nerve of the forearm; the former especially can be entrapped. The median nerve
remains anterior of the elbow in its course and passes between the two heads of the pronator muscle and can also become entrapped. The ulnar nerve passes through the triceps fascia as it approaches the cubital tunnel on the medial posterior aspect of the elbow, where it can be compressed and cause distal problems.

The elbow joint can be moved about a longitudinal and transverse axis. Flexion-extension is provided by the humeroulnar joint. The rotational motion is provided by the unique articulation of the radius with the
capitellum portion of the humerus and the ulna so that forearm pronation and supination can be carried out.

The normal range of motion of the elbow is flexion and extension 0–145° with a functional arc of 0– 130°. Pronation and supination can be carried out with 70–90° of pronation to 90° of supination. The axial
rotation is around the center of the radial head.

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