Anconeus
A small triangular muscle at the back of the elbow, often described as a fourth head of the triceps.
- Type
- Muscle
- Region
- Arm
- Standard name
- m. anconeus
- Origin
- Posterior surface of the lateral epicondyle of the humerus
- Insertion
- Lateral surface of the olecranon and the upper posterior ulna
- Actions
- elbow extensionelbow stabilisation
- Verify
- TA2 2510 TA98 A04.6.02.023
What it is
A small triangular muscle spanning the back of the elbow, from the outer bump of the humerus to the upper ulna. It is continuous with the medial head of triceps brachii, and some anatomists describe it as a fourth triceps head rather than a separate muscle.
It shares its nerve supply with triceps, which supports that reading.
What it does
Assists elbow extension, weakly.
Its more interesting suggested role is stabilising the elbow — specifically, resisting the tendency of the ulna to be pulled sideways during forearm rotation, and tensioning the joint capsule so it is not pinched as the elbow straightens. That role is plausible and described in the literature, and the size of its actual contribution is not well quantified.
What loads it
Elbow extension, alongside triceps. Nothing loads it separately.
What is commonly got wrong about it
That it matters for arm size or strength. It is small, weak, and shares its job with a much larger muscle.
That "tennis elbow" is an anconeus problem. Lateral elbow pain is usually attributed to the common extensor tendon nearby, particularly extensor carpi radialis brevis. Either way it is a clinical question and not something to train through.