[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/) › Anconeus

[Muscular system](https://durgical.com/en/anatomy/system/muscular-system/) · [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/)

# Anconeus

The anconeus is a small triangular muscle on the outer back of the elbow; it helps straighten and steady the elbow.

[See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=upper_limb&select=anconeus&side=r)

Opens in the Durgical app, no sign-up needed.

## What it is

A small triangular muscle on the outer back of the elbow.

## What it does

Helps straighten and steady the elbow.

## Key points

- The Kocher approach to the radial head uses the interval between the anconeus ([radial nerve](https://durgical.com/en/anatomy/radial-nerve/)) and the extensor carpi ulnaris ([posterior interosseous nerve](https://durgical.com/en/anatomy/posterior-interosseous-nerve/))
- Covers the lateral 'soft spot' of the elbow, between the lateral epicondyle, radial head and olecranon tip, used to aspirate or inject the joint
- Works as a continuation of the triceps (medial head), whose nerve it shares, and steadies the lateral side of the joint

## Key facts

**Origin**
Lateral epicondyle

**Insertion**
Lateral olecranon and upper posterior ulna

**Action**
Helps extend the elbow; steadies the ulna in pronation

**Nerve**
Radial nerve (C7–C8)

**Blood supply**
Middle collateral artery, recurrent interosseous artery

## Relations

**Lateral**
ECU, [extensor carpi ulnaris](https://durgical.com/en/anatomy/extensor-carpi-ulnaris/) (the Kocher interval)

**Deep**
[Elbow capsule](https://durgical.com/en/anatomy/elbow-joint-capsule/), [annular ligament](https://durgical.com/en/anatomy/annular-ligament-of-the-radius/), radial head, LUCL and the [supinator](https://durgical.com/en/anatomy/supinator/)

**Above**
[Triceps (medial head)](https://durgical.com/en/anatomy/triceps-brachii-medial-head/), whose lower fibres blend with it

**Medial**
Olecranon and the subcutaneous posterior border of the [ulna](https://durgical.com/en/anatomy/ulna/)

## How to find it

Felt in the triangular soft area at the back of the elbow, between the lateral epicondyle, the tip of the olecranon and the radial head; it tightens when the elbow is straightened or the forearm pronated against resistance.

## On imaging

A small triangular muscle at the back of the lateral elbow, seen on axial MRI between the olecranon and the lateral epicondyle. The lateral soft spot it covers is where an elbow effusion bulges: ultrasound shows the fluid there and guides aspiration. On MRI it is checked alongside the common extensor origin in lateral elbow pain.

## Clinical notes

- Pronating the forearm during the Kocher approach moves the posterior interosseous nerve away from the radial neck
- A needle in the soft spot passes through the anconeus to drain blood from a radial head fracture or fluid from the joint
- It can be turned as a small local muscle flap to cover defects around the olecranon
- Not to be confused with the anconeus epitrochlearis, an accessory muscle over the cubital tunnel in some people that can compress the [ulnar nerve](https://durgical.com/en/anatomy/ulnar-nerve/)

## Development

Forms with the dorsal mass and is often treated as a distal continuation of the medial head of triceps; the branch that supplies it runs down through that head.

## Test yourself

Think of the answer, then tap the question to see it.

## Which interval does the Kocher approach to the radial head use?

Between the anconeus (radial nerve) and the extensor carpi ulnaris (posterior interosseous nerve).

## What is the lateral soft spot of the elbow, and what is it used for?

The area over the anconeus between the lateral epicondyle, radial head and olecranon tip; used to aspirate or inject the joint.

## Why is the forearm pronated during the Kocher approach?

Pronation moves the posterior interosseous nerve away from the radial neck.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/anconeus/)

Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
musculus anconeus TA2 2510

**Official Spanish (DeCS)**
Músculo ancóneo

**English (TA2)**
Anconeus

## Related

- [Radial nerve](https://durgical.com/en/anatomy/radial-nerve/)
- [Humerus](https://durgical.com/en/anatomy/humerus/)
- [Ulna](https://durgical.com/en/anatomy/ulna/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb, Arm Muscles](https://www.ncbi.nlm.nih.gov/books/NBK554420/); [Anatomy, Shoulder and Upper Limb, Elbow Joint](https://www.ncbi.nlm.nih.gov/books/NBK532948/).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/anatomy/anconeus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/anconeus/