Extensor Carpi Radialis Brevis
Forearm · Upper Limb
The extensor carpi radialis brevis lies deep and medial to its longer partner and shares the same actions. It arises from the lateral epicondyle of the humerus through the common extensor origin and inserts on the base of the third metacarpal. It extends and abducts (radially deviates) the wrist and stabilises it during gripping. It is supplied by the deep branch of the radial nerve (C7, C8). Its origin at the common extensor tendon makes it a key player in lateral epicondylitis, or tennis elbow.
Origin, Insertion, Action & Nerve
Origin
Lateral epicondyle of humerus (common extensor origin)
Insertion
Base of 3rd metacarpal
Action
Extension and abduction (radial deviation) of wrist
Nerve
Deep branch of radial nerve (C7, C8)
Attachments explained
The Extensor Carpi Radialis Brevis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Lateral epicondyle of humerus (common extensor origin)
Insertion
Base of 3rd metacarpal
Action & function
When the Extensor Carpi Radialis Brevis contracts, it produces the following movement: Extension and abduction (radial deviation) of wrist.
As part of the Forearm group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Extensor Carpi Radialis Brevis receives its nerve supply from the Deep branch of radial nerve (C7, C8). This nerve carries fibres from spinal segment(s) C7, C8.
Because a muscle can only contract when its nerve is intact, injury to the Deep branch of radial nerve or to its spinal roots (C7, C8) can weaken or paralyse the Extensor Carpi Radialis Brevis, impairing the movements it normally produces (extension and abduction (radial deviation) of wrist). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Extensor Carpi Radialis Brevis (the OIANS method)
Study the brevis as the shorter twin of the longus: same actions of wrist extension and radial deviation, but arising from the common extensor tendon at the lateral epicondyle and inserting one metacarpal over, on the third. Learning the pair together, differing only in origin and insertion point, is the efficient approach.
Its memorable clinical link is tennis elbow: because it arises from the common extensor origin at the lateral epicondyle, overuse strains that tendon and produces lateral epicondylitis. Noting that it is supplied by the deep branch of the radial nerve, whereas the longus takes the main trunk, distinguishes the two.
Frequently asked questions
Where is the Extensor Carpi Radialis Brevis located?
The Extensor Carpi Radialis Brevis is a muscle of the Forearm group, located in the Upper Limb.
What is the origin of the Extensor Carpi Radialis Brevis?
Lateral epicondyle of humerus (common extensor origin)
What is the insertion of the Extensor Carpi Radialis Brevis?
Base of 3rd metacarpal
What movements does the Extensor Carpi Radialis Brevis produce?
Extension and abduction (radial deviation) of wrist
What nerve supplies the Extensor Carpi Radialis Brevis?
Deep branch of radial nerve (C7, C8)
Is the Extensor Carpi Radialis Brevis free to study in OIANS?
Yes. The Extensor Carpi Radialis Brevis is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Extensor Carpi Radialis Brevis
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