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# Radial head cartilage

The radial head cartilage covers the top of the [radius](https://durgical.com/en/anatomy/radius/) at the elbow; it lets the radius spin against the humerus and ulna as the forearm turns.

Official name: Cartilage of the radial head

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## What it is

The smooth cap on the disc-shaped top of the radius.

## What it does

Lets the radius spin against the humerus and ulna when the forearm turns.

## Key points

- Covers the concave top (on the capitulum) and most of the rim (in the radial notch and annular ligament); the uncovered arc of the rim, facing laterally with the forearm in neutral, is the 'safe zone' for plates
- Radial head fractures are the most common elbow fractures in adults; the Mason classification grades them: I undisplaced, II displaced partial-head, III comminuted (IV with a dislocation)
- A secondary stabiliser against valgus stress and a major load path: much of the force from the wrist passes through it to the capitulum

## Key facts

**Where**
Concave top and rim of the radial head

**Function**
Glides on the capitulum and turns in the radial notch and annular ligament

## Relations

**Above**
Capitulum of the [humerus](https://durgical.com/en/anatomy/humerus/), across the radiocapitellar joint

**Medial**
Radial notch of the [ulna](https://durgical.com/en/anatomy/ulna/), forming the proximal radioulnar joint

**Lateral**
[Annular ligament](https://durgical.com/en/anatomy/annular-ligament-of-the-radius/) encircling the rim, with the [RCL (elbow)](https://durgical.com/en/anatomy/radial-collateral-ligament-of-the-elbow/) and the [supinator](https://durgical.com/en/anatomy/supinator/) over it

**Below**
Radial neck, where the [posterior interosseous nerve](https://durgical.com/en/anatomy/posterior-interosseous-nerve/) winds round to enter the supinator

**Behind**
[Anconeus](https://durgical.com/en/anatomy/anconeus/) and the LUCL (lateral ulnar collateral ligament)

## How to find it

It lies in the lateral 'soft spot', the triangle between the lateral epicondyle, the radial head and the tip of the olecranon. A thumb placed just below the lateral epicondyle feels the head turn as the forearm is pronated and supinated; the same spot is used for elbow aspiration and an arthroscopy portal.

## On imaging

AP and lateral X-rays, plus a radiocapitellar (Greenspan) oblique view that projects the head clear of the coronoid. After trauma, a lifted anterior fat pad ('sail') or any visible posterior fat pad means an effusion and, in an adult, a likely hidden radial head fracture.

## Clinical notes

- Essex-Lopresti injury: a radial head fracture with tearing of the interosseous membrane and the distal radioulnar joint; removing the head then lets the radius migrate upward, so it is fixed or replaced rather than excised
- The posterior interosseous nerve crosses the radial neck: lateral approaches are made with the forearm pronated, which moves the nerve forward and away
- In the terrible triad (posterior elbow dislocation with radial head and coronoid fractures) the radial head is fixed or replaced to restore stability

## Development

Its ossification centre appears in early childhood (the 'R' of CRITOE); children tend to fracture the radial neck rather than the head, and the physis below the head can be mistaken for a fracture.

## Related conditions

- [Radial head subluxation (pulled elbow)](https://durgical.com/en/conditions/radial-head-subluxation/)

## Test yourself

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

## What are the most common elbow fractures in adults, and how are they graded?

Radial head fractures, graded by Mason: I undisplaced, II displaced partial-head, III comminuted, IV with a dislocation.

## Which nerve crosses the radial neck, and how is it protected in lateral approaches?

The posterior interosseous nerve; the forearm is pronated, which moves the nerve forward and away.

## After elbow trauma in an adult, what does a visible posterior fat pad suggest?

An effusion and a likely hidden radial head fracture.

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

## Its names

**Official Latin (TA2)**
cartilago articularis capitis radii TA2 382

**Official Spanish (DeCS)**
Cartílago articular de la cabeza del radio

**English (TA2)**
Cartilage of the radial head

## Related

- [Radius](https://durgical.com/en/anatomy/radius/)
- [Ulna](https://durgical.com/en/anatomy/ulna/)

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

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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/cartilage-of-the-radial-head/