|Back of right upper extremity. (Anconeus labeled at bottom center.)|
|Posterior surface of the forearm. Superficial muscles. (Anconeus visible at center right.)|
|Gray's||subject #125 454|
|Origin||lateral epicondyle of the humerus proximally|
|Insertion||lateral surface of the olecranon process and the superior part of the posterior ulna distally|
|Artery||deep brachial artery, recurrent interosseous artery|
|Nerve||radial nerve (C7, C8, and T1)|
|Actions||It is partly blended in with the triceps, which it assists in extension of the forearm. It also stabilizes the elbow during pronation and supination and pulls slack out of the elbow joint capsule during extension to prevent impingement.|
Some consider anconeus to be a continuation of the triceps brachii muscle. Some sources consider it to be part of the posterior compartment of the arm, while others consider it part of the posterior compartment of the forearm.
The anconeus muscle can easily be palpated just lateral to the olecranon process of the ulna.
Origin and insertion
Anconeus originates on the posterior surface of the lateral epicondyle of the humerus and is inserted on the ulna lateral to the olecranon from where it extends down on the dorsal side of the bone. 
Its function is trivial in humans. It assists in extension of the elbow, where the triceps brachii is the principal agonist, and supports the elbow in full extension. It also prevents the elbow joint capsule being pinched in the olecranon fossa during extension of the elbow. Anconeus also abducts the ulna and stabilizes the elbow joint.
Anconeus is innervated by the radial nerve (cervical roots 7 and 8) from the posterior cord of the brachial plexus. The somatomotor portion of radial nerve innervating anconeus bifurcates from the main branch in the radial groove of the humerus. This innervation pattern follows the rules of innervation of the musculature of the posterior forearm (extensor) compartment by the radial nerve.
Pathology: Trauma to the anconeus muscle can usually result from a shoulder dislocation or fractures of the upper part of the humerus or around the olecranon, or any injury that damages the radial nerve. Harm inflicted upon the radial nerve through these mechanisms can paralyze the anconeus muscle as well as other extensors of the elbow and wrist. There are no specific acquired injuries that exclusively affect the anconeus muscle; however, any disease that compromises muscular functions, particularly arm extension (i.e. muscular dystrophy) will affect this particular accessory muscle. Heterotrophic ossification can result from certain trauma as it is an abnormal growth of osseous tissue in non-osseous tissue (e.g. muscle tissue). The condition is usually found in the hips, although there have been documented cases of certain individuals with it occurring in the arms and legs. The cause for the process to initiate is not well understood, only that it typically results from surgery or trauma.
- Williams, P. et al., 1995, Gray's Anatomy, 38th ed., Churchill Livingstone
- Jones, W. et al.(eds) , 1953, Buchanan's Manual of Anatomy, 8th ed., Balliére, Tindall and Cox., pp. 496
- Grant, J. & Basmajian J., 1965, Grant's Method of Anatomy, 7th ed., The Williams & Wilkins Company, Baltimore, pp. 163-164
- "Dissector Answers — Axilla & Arm". Archived from the original on 3 January 2008. Retrieved 2008-01-17.
- "The Radius and Ulna". Archived from the original on 2008-06-11. Retrieved 2008-01-17.
- "Anconeus". The Hosford Muscle Tables. Retrieved February 2012.