Extensor pollicis brevis muscle

Last revised by Tom Foster on 9 Jun 2022

Extensor pollicis brevis (EPB) muscle is one of the muscles of the deep layer of the posterior compartment of the forearm, inserting into the base of the proximal phalanx of the thumb. Along with extensor pollicis longus, it is responsible for extension of the thumb. Along with abductor pollicis longus it passes through the 1st extensor compartment of the wrist. It is one of the extrinsic muscles of the hand.


  • origin: posterior surface of distal radial shaft and interosseous membrane
  • insertion: dorsal surface base of the proximal phalanx of the thumb
  • action: extends the thumb at metacarpophalangeal joint
  • arterial supply: posterior interosseous artery
  • innervation: posterior interosseous nerve (C7 and C8), a continuation of the deep branch of the radial nerve (C7, C8)

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