The anconeus is a small, triangular muscle located near the elbow joint. This muscle occupies a shallow position at the back of the elbow, making it accessible to palpation in many individuals. Although relatively small, the anconeus plays a role that extends beyond simple movement, contributing to the overall stability of the elbow structure. Understanding its specific location and function is important for arm mechanics.
Exact Location and Structure
The anconeus muscle is situated on the posterior side of the elbow joint, forming a small triangular shape that spans the space between the humerus (upper arm bone) and the ulna (forearm bone). It originates by a tendon from the posterior surface of the lateral epicondyle of the humerus, which is the prominent bony knob on the outside of the upper arm near the elbow. This origin point is just above the common extensor tendon.
From its origin, the muscle fibers extend obliquely downward and medially. The muscle then inserts onto the ulna, specifically attaching to the lateral surface of the olecranon process and the superior proximal part of the posterior surface of the ulnar shaft. Due to its position, some anatomists consider the anconeus a continuation of the larger triceps brachii muscle, with fibers often blending together.
Primary Role in Movement
The main action of the anconeus muscle is to assist in the extension of the forearm, which involves straightening the elbow joint. While the larger triceps brachii muscle is the primary mover for this action, the anconeus acts as a weak accessory extensor. This muscle is innervated by the radial nerve, which also supplies the other extensor muscles of the arm and forearm.
Beyond extension, the anconeus functions as a dynamic stabilizer of the elbow joint. It helps stabilize the elbow during forearm movements like pronation and supination, such as turning a screwdriver. During extension, it pulls the slack out of the posterior elbow joint capsule. This action prevents the joint capsule from being pinched or impinged within the olecranon fossa, the bony depression at the back of the humerus.
When the Anconeus Causes Trouble
The anconeus muscle’s location near the lateral epicondyle means it is often implicated in conditions involving lateral elbow pain. Although the primary muscles involved in lateral epicondylitis (Tennis Elbow) are the wrist extensors, the anconeus can be secondarily affected. Studies using magnetic resonance imaging have shown that patients with chronic lateral epicondylitis frequently exhibit an increased signal intensity within the anconeus muscle. This finding suggests the muscle is involved in the inflammation or swelling associated with the condition.
Irritation of the anconeus muscle itself, sometimes called “Anconeus syndrome,” can be the main cause of lateral elbow pain. This specific muscle strain may not respond to standard treatments for general lateral epicondylitis. Symptoms often include pain localized to the back and outer side of the elbow, which requires specific evaluation for diagnosis.
Recovery typically focuses on rest and reducing inflammation, often followed by physical therapy. Treatment may include using an elbow splint and strengthening exercises targeting the elbow and wrist. In rare instances of chronic issues, surgical procedures have been used, such as transposing the anconeus muscle to cover the exposed joint area, which has successfully alleviated pain in some patients.