Anconeus

What is the Anconeus

The anconeus is a small muscle in the arm involved in the extension of the elbow. It is sometimes included in the superficial extensor group in the posterior compartment of the forearm along with brachioradialis, extensor carpi radialis longus, and brevis, extensor digiti minimi, extensor digitorum, and extensor carpi ulnaris. On the other hand, some count it as one of the two extensors of the upper arm, along with the triceps, since the muscle can be considered a continuation of the latter.

Location and Anatomy

Origin	The dorsal side of the lateral epicondyle of the humerus
Insertion	The olecranon, and along the upper one-third portion at the back of the ulna

After originating, the muscle tendons spread out to form a broad muscle belly which then inserts into the olecranon. It party attaches to the posterior humeroulnar joint capsule as well.

The muscle fibers may blend partially or completely with the triceps brachii or sometimes with the extensor carpi ulnaris.

Functions

Action

Extension of the forearm at the elbow joint

The primary role of the anconeus is to assist the triceps brachii in its actions. So, like the triceps, contraction of the anconeus straightens the elbow joint. 

Since it has an extended attachment to the ulna, studies have been conducted to find out whether it has any role in the movements of the ulna. They have shown it to help in abducting and pronating the ulna, keeping it stabilized during movements like rotating a knob, or using a screwdriver.

Innervation

Nerve

Radial nerve (C6, C7, C8)

Since it is often partly blended with the triceps brachii, the two muscles are innervated by the same nerve branches.

The T1 branch of radial nerve innervates the skin that covers the anconeus muscle.

Blood Supply

Artery

The recurrent interosseous, and deep brachial arteries