Flexor digitorum profundus muscle

Last revised by Dr Mostafa El-Feky on 12 Aug 2022

Flexor digitorum profundus (FDP) muscle makes up the third layer of the anterior compartment of the forearm along with flexor pollicis longus muscle. It passes through the carpal tunnel. It is one of the extrinsic muscles of the hand.


  • origin: 
    • medial olecranon, upper three-quarters of the anterior and medial surface of ulna, adjacent interosseous membrane
    • shares aponeurotic attachment to the posterior border of the ulna with flexor & extensor carpi ulnaris
  • insertion: volar surface of distal phalanges of the second to fifth fingers
  • innervation
  • action: flexion at the distal interphalangeal, proximal interphalangeal and wrist joints

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Cases and figures

  • Figure 1: carpal tunnel diagram
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  • Figure 2: carpal tunnel diagram
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