The anconeus is a small triangular muscle on the posterolateral elbow extending from the lateral epicondyle to the olecranon, acting as an accessory elbow extensor and elbow joint stabiliser during forearm rotation. It is always active during elbow movements, serving as the elbow's stabilising muscle analogous to the rotator cuff at the shoulder, preventing the elbow joint capsule from being pinched during movement.
| Origin | Posterior surface of the lateral epicondyle of the humerus |
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| Insertion | Lateral surface of the olecranon and upper posterior ulna |
| Nerve Supply | Radial nerve (C7, C8) |
| Blood Supply | Posterior interosseous artery; Recurrent interosseous artery |
| Actions | Weak extension of the elbow; Abduction of the ulna during forearm pronation; Stabilises the elbow joint during forearm rotation |
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By abducting the ulna during forearm pronation it prevents the medial ulnar border from impinging against the trochlea during rotation, acting as a dynamic joint protector throughout forearm movement.
The anconeus is routinely included in the Kocher approach to the lateral elbow, where the interval between the anconeus and extensor carpi ulnaris provides safe access to the posterior lateral elbow without endangering the posterior interosseous nerve. Anconeus compartment syndrome can occur after elbow trauma. Its EMG activity as a tonically active elbow stabiliser makes it useful for EMG biofeedback in elbow rehabilitation.
The anconeus is palpable as a small triangular muscle belly filling the triangular space posterolaterally between the lateral epicondyle, olecranon, and the posterior border of the ulna, becoming firm during resisted elbow extension.
Rare acute muscle injury from forceful elbow extension producing posterolateral elbow pain reproduced by resisted extension, managed conservatively.
