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# Triceps (medial head)

The medial head of the triceps is the deep part of the triceps, mostly hidden by the other two heads; it straightens the elbow in every position.

Official name: Triceps brachii, medial head

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## What it is

The deep head of the triceps, against the humerus.

## What it does

Straightens the elbow in every position.

## Key points

- The deep head: below the radial groove and covered by the long and lateral heads, except just above the elbow on both sides of the tendon
- The ulnar nerve runs down on its medial surface behind the medial intermuscular septum; a branch of the radial nerve to this head travels with the ulnar nerve
- The nerve to the [anconeus](https://durgical.com/en/anatomy/anconeus/) runs through this head; the anconeus is often described as its continuation

## Key facts

**Origin**
Posterior humerus below the radial groove; lower medial and lateral intermuscular septa

**Insertion**
Olecranon

**Action**
Extends the elbow

**Nerve**
Radial nerve (C6–C8)

**Blood supply**
Deep brachial artery

## Relations

**Superficial**
[Triceps (long head)](https://durgical.com/en/anatomy/triceps-brachii-long-head/) and [triceps (lateral head)](https://durgical.com/en/anatomy/triceps-brachii-lateral-head/)

**Deep**
Back of the [humerus](https://durgical.com/en/anatomy/humerus/) below the radial groove; near the elbow, the olecranon fossa and posterior [elbow capsule](https://durgical.com/en/anatomy/elbow-joint-capsule/), to which deep fibres attach

**Medial**
[Ulnar nerve](https://durgical.com/en/anatomy/ulnar-nerve/) and the superior ulnar collateral artery, behind the medial intermuscular septum

**Above**
[Radial nerve](https://durgical.com/en/anatomy/radial-nerve/) and [deep brachial artery](https://durgical.com/en/anatomy/deep-brachial-artery/) in the radial groove

## How to find it

Felt just above the elbow on either side of the [triceps tendon](https://durgical.com/en/anatomy/triceps-tendon/), especially medially, as the elbow is straightened against resistance from a bent position.

## Examination

- Palpation behind the medial epicondyle while the elbow bends: a second snap after the ulnar nerve's points to a snapping medial head of triceps; the nerve alone gives one

## On imaging

Deep to the long and lateral heads; on axial MRI it wraps the back of the distal humerus, with the ulnar nerve on its medial side. Distal triceps tendon tears are uncommon; the lateral radiograph may show a small flake of bone pulled off the olecranon (flake sign), and ultrasound or MRI show the tendon gap.

## Clinical notes

- Snapping triceps: part of the medial head slips over the medial epicondyle on flexion, often with the ulnar nerve, and can be mistaken for ulnar nerve subluxation
- Deep fibres pull the posterior capsule away so it is not pinched in extension
- Approaches that split this head near the elbow can cut the nerve to the anconeus

## Related conditions

- [Olecranon bursitis](https://durgical.com/en/conditions/olecranon-bursitis/)

## Test yourself

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

## Where does the medial head of triceps arise, and how is it covered?

From the posterior humerus below the radial groove; the long and lateral heads cover it except just above the elbow.

## What is a snapping triceps, and what is it mistaken for?

Part of the medial head slips over the medial epicondyle on flexion; it is mistaken for ulnar nerve subluxation.

## Which nerve runs down the medial surface of the medial head of triceps?

The ulnar nerve, behind the medial intermuscular septum, with the superior ulnar collateral artery.

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

## Its names

**Official Latin (TA2)**
caput mediale musculi tricipitis brachii TA2 2474

**Official Spanish (DeCS)**
Cabeza medial del músculo tríceps braquial

**English (TA2)**
Triceps brachii, medial head

**Also called**
deep head of triceps

## Related

- [Radial nerve](https://durgical.com/en/anatomy/radial-nerve/)
- [Deep brachial artery](https://durgical.com/en/anatomy/deep-brachial-artery/)
- [Humerus](https://durgical.com/en/anatomy/humerus/)
- [Triceps tendon](https://durgical.com/en/anatomy/triceps-tendon/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb, Triceps Muscle](https://www.ncbi.nlm.nih.gov/books/NBK536996/).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/triceps-brachii-medial-head/