Some consider anconeus to be a continuation of the triceps brachii muscle.
The " anconeus " is a small muscle that stabilizes the elbow joint during movement.
The brachioradialis is synergistic with the brachialis and biceps brachii; the triceps brachii and anconeus are antagonistic.
In humans, the anconeus is sometimes loosely called " the fourth head of the triceps brachii ".
It is also known as the " subanconeus muscle ", for its relationship to the anconeus muscle.
The muscles of this compartment are the triceps brachii and anconeus muscle and these are innervated by the radial nerve.
Muscles contributing to function are all flexion ( biceps brachii, brachialis, and brachioradialis ) and extension muscles ( triceps and anconeus ).
Also, brachioradialis, anconeus, triceps brachii, and extensor carpi radialis longus are all innervated by muscular branches of the radial nerve in the arm.
The brachioradialis, flexor of the anconeus, assisting in extension of the elbow joint, is by some considered part of the posterior compartment of the arm.
Extension in the humeroulnar joint is produced by the triceps brachii and anconeus muscle, with a tiny contribution from the muscles arising from the lateral epicondyle of the humerus, such as the extensor digitorum muscle.