Overview

The brachioradialis is the prominent muscle along the thumb side of the forearm. Despite living mostly in the forearm, its main job is to bend the elbow.

It works especially well when the forearm is in a neutral, thumb-up position—the grip used for a hammer curl, carrying a suitcase or lifting a mug. It can also help bring the forearm back toward neutral after the palm has turned fully up or down.

Location

Begins on the outer lower humerus above the elbow
Crosses the elbow without crossing the wrist
Runs down the thumb side of the forearm to the radius

Origin, Insertion, Nerve Supply, and Action

Origin: Proximal two-thirds of the lateral supracondylar ridge of the humerus
Insertion: Lateral distal radius near the styloid process
Nerve supply: Radial nerve, mainly C5–C7
Action: Flexes the elbow most effectively with the forearm in neutral

Function

Bends the elbow during neutral-grip lifting
Helps return the forearm toward neutral from full pronation or supination
Assists the biceps and brachialis during carrying and pulling

Common Problems

The brachioradialis can become sore after a sharp increase in hammer curls, climbing, gripping or repetitive tool use. Pain is often felt near the outer elbow or along the upper thumb-side forearm.

That location overlaps with tennis elbow, radial-nerve irritation and other forearm muscles. A tender spot or painful curl cannot diagnose the source on its own.

When to Get It Assessed

Arrange an assessment if pain follows a sudden injury, grip or wrist strength is clearly reduced, numbness or tingling develops, or symptoms continue despite reducing the aggravating load.

References

OpenStax. “Muscles of the Pectoral Girdle and Upper Limbs.” https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs
Moore KL et al. Clinically Oriented Anatomy. Wolters Kluwer.
Standring S, ed. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. Elsevier.

Brachioradialis