Flexor carpi ulnaris muscle

Last revised by Daniel J Bell on 16 Jan 2021

Flexor carpi ulnaris (FCU) muscle is of the first layer of the anterior compartment of the forearm. It is one of the extrinsic muscles of the hand.


  • origin
    • humeral head: medial epicondyle of the humerus
    • ulnar head: aponeurosis from medial olecranon and upper three quarters subcutaneous border of ulna
  • insertion: base of 5th metacarpal; hook of hamate, pisiform
  • arterial supply: posterior ulnar recurrent artery and ulnar artery
  • innervationulnar nerve (C8-T1)
  • action: flexion and adduction of the wrist joint
  • pathology: calcific tendinitis which occurs at the insertion into pisiform
  • variability: muscle can be doubled - accessory flexor carpi ulnaris muscle, which can be often accompanied by concomitant variants 3

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