Flexor Carpi Ulnaris

  • Origin: Humeral head: Humerus (medial epicondyle via common flexor tendon)
    Ulnar head: Ulna (olecranon, medial margin; shaft, proximal 2/3 posterior via an aponeurosis)
    Intermuscular septum
  • Insertion: Pisiform
    Hamate
    5th metacarpal, base
    Flexor retinaculum
  • Innervation: Cervical roots): C7-T1
    Nerve: ulnar nerve
  • At distal volar wrist crease the ulnar artery and nerve are radial to the FCU tendon.
  • The FCU muscle has two heads. The ulnar nerve can be entrapped proximally between the two heads.
  • The FCU muscle tendon unit is in the superficial group of volar forearm muscles.
  • The FCU muscle is the only volar forearm muscle completely and only innervated by the ulnar nerve.
Diagrams & Photos
  • The flexor carpi ulnaris (FCU) tendon is one of the three muscles in the superficial compartment of the volar forearm.
    The flexor carpi ulnaris (FCU) tendon is one of the three muscles in the superficial compartment of the volar forearm.
  • The flexor carpi ulnaris (FCU) tendon has been split to expose the pisiform. Note the ulnar nerve and artery.
    The flexor carpi ulnaris (FCU) tendon has been split to expose the pisiform. Note the ulnar nerve and artery.
Key Points
  • The flexor carpi ulnaris (FCU) muscle is the most powerful wrist flexor.
  • The pisiform is a sesamoid-like bone surrounded by the FCU tendon.
  • The pisiform forms the ulnar side of Guyon’s canal.
  • There is internervous plane between the flexor carpi ulnaris (FCU) and the extensor carpi ulnaris (ECU) which provides a safe route for ulnar shaft exposure during ORIF of ulnar fractures.
  • The dorsal ulnar sensory nerve passes through or just distal to the FCU muscle as it travels to the dorsum of the ulnar wrist and hand.
Anatomy References
Anatomic Abbreviations
Hand Surgery Resource Anatomy Diagnostic Guide (Chapter)