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Flexor pollicis longus




Flexor pollicis longus - anterior view
Flexor pollicis longus - anteromedial view

General information

  • This section is strictly limited to anatomy, you might be looking for clinical relevant information which is found under the clinical chapters -- muscles section, click here to go to that page
  • A part of the lower arm's anterior deep muscle group


  • Deep


  • Anterior surface of proximal radius (just distally to tuberositas radii)
  • Interosseus membrana
  • Processus coroneideus ulna
  • Medial epicondyle humerus


  • Anterior surface of distal phalanx of thumb

Main function

  • Wrist
    • Flexion
  • CMC
    • Flexion
  • MCP
    • Flexion
  • IP
    • Flexion

Secondary function

  • Elbow
    • Flexion
  • Wrist
    • Radial deviation

Nerve innervation

  • Segmental
    • C7-Th1
  • Peripheral
    • Median nerve

Arterial supply

  • Radial artery
  • Anterior interosseus artery


  • Patient position
    • Sitting or supine
  • Localize the muscle belly of flexor carpi radialis and brachioradialis
  • Ask the patient to flex the IP-joint of the thumb
  • Feel for the contraction between flexor carpi radialis and brachioradialis in the middle of the anterior aspect of the lower arm

Strength test

  • Patient position
    • Sitting or supine
  • Fixate the MCP joint by the patient's thumb
  • Give resistance towards the palmar surface of the distal phalanx in the direction of extension so that the patient is giving force towards flexion
  • Have the patient maintain the position of the thumb throughout the testing