CorpusHuman Anatomy
MuscularMuscle

Extensor pollicis brevis

Musculus extensor pollicis brevis

Also known as: EPB

A deep posterior forearm muscle that extends the thumb at the MCP joint. With APL, it forms the anterior (radial) border of the anatomical snuffbox.

Show on body map Muscles — Posterior View

Overview

EPB arises from the posterior surface of the radius and the interosseous membrane, distal to APL, whose medial side it follows. Its tendon shares the 1st extensor compartment with APL and inserts on the base of the proximal phalanx of the thumb. It extends the thumb at the MCP (and CMC) joints. Together with APL it forms the radial border of the anatomical snuffbox, and it is involved in De Quervain tenosynovitis.

Anatomy

Origin

Posterior surface of the radius and the interosseous membrane.

Insertion

Dorsal base of the proximal phalanx of the thumb.

Action

Extension of the thumb at the metacarpophalangeal joint.

Innervation

Posterior interosseous nerve.

Nerve roots

C7–C8

Arterial supply

Posterior interosseous artery.

Function

  • Extends the thumb at the MCP and CMC joints

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.