Extensor Carpi Radialis Brevis Muscle – Functions, Anatomy

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 3 min read
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Article Summary

The Extensor Carpi Radialis Brevis Muscle is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis. Extensor carpi radialis brevis is a fusiform muscle found in the lateral part of the posterior forearm. Together with anconeus, brachioradialis, extensor carpi radialis longus, extensor digitorum, extensor...

Key Takeaways

  • This article explains Origin and Insertion of Extensor Carpi Radialis Brevis Muscle in simple medical language.
  • This article explains Anatomy of Extensor Carpi Radialis Brevis Muscle in simple medical language.
  • This article explains Nerve Supply of Extensor Carpi Radialis Brevis Muscle in simple medical language.
  • This article explains Blood Supply of Extensor Carpi Radialis Brevis Muscle in simple medical language.
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Definition

The Extensor Carpi Radialis Brevis Muscle is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis.

Extensor carpi radialis brevis is a fusiform muscle found in the lateral part of the posterior forearm. Together with anconeus, brachioradialis, extensor carpi radialis longus, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris, it belongs to the superficial forearm extensor group. Crossing the elbow and wrist joints from their posterior aspects, these muscles produce extension at one or both of these joints. The specific action of extensor carpi radialis brevis is to extend and abduct the hand at the wrist joint.

Origin and Insertion of Extensor Carpi Radialis Brevis Muscle

It arises from the lateral epicondyle of the , by the common extensor ; from the radial collateral  of the elbow-joint; from a strong aponeurosis which covers its surface; and from the intermuscular septa between it and the adjacent muscles.[rx]

The fibers end approximately at the middle of the forearm in the form of a flat tendon, which is closely connected with that of the extensor carpi radialis longus, and accompanies it to the wrist; it passes beneath the abductor pollicis longus and extensor pollicis brevis, beneath the extensor retinaculum, and inserts into the lateral dorsal surface of the base of the third bone, with a few fibers inserting into the medial dorsal surface of the second metacarpal bone.[rx]

of Extensor Carpi Radialis Brevis Muscle

Extensor carpi radialis brevis
  • Origin: lateral epicondyle of humerus
  • Insertion: base of 3rd metacarpal
  • Action: extension and abduction of the wrist
  • Innervation: radial nerve

Nerve Supply of Extensor Carpi Radialis Brevis Muscle

  • Like all the muscles in the posterior forearm, ECR Brevis is supplied by a branch of the radial nerve.
  • Extensor carpi radialis brevis is innervated directly by the radial nerve (C5- C8), or sometimes from its deep branch/posterior interosseous nerve. The radial nerve stems from the posterior cord of the brachial plexus.

Blood Supply of Extensor Carpi Radialis Brevis Muscle

  • The muscle is vascularized by the radial , radial artery and deep brachial artery (via its radial collateral branch).

Function of Extensor Carpi Radialis Brevis Muscle

  • It is an extensor, and an abductor of the hand at the wrist joint. That is, it serves to manipulate the wrist so that the hand moves away from the palm and towards the thumb. The muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension. A wrist roller can be used and reverse wrist curls with dumbbells can be performed.
  • When the extensor carpi radialis brevis muscle contracts together with extensor carpi radialis longus and flexor carpi radialis, it contributes to producing hand abduction (radial deviation).
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Doctor to discuss: Doctor / qualified healthcare provider
Tests to discuss with doctor
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Questions to ask
  • What is the most likely cause of my symptoms?
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Go to emergency care if you notice:
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Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

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  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.