The flexor carpi ulnaris muscle is one of 4 muscles within the superficial layer of the anterior compartment of the forearm, and is responsible for flexion and adduction at the wrist joint. The other muscles in this layer are the palmaris longusflexor carpi radialis and pronator teres. The muscles of the superficial layer share a common origin from the medial epicondyle of the humerus.

It is the most medially located muscle within the superficial layer of forearm flexors. It has two heads:

  • Humeral head
  • Ulnar head

The flexor carpi ulnaris muscle is the only muscle in the anterior compartment of the forearm, together with the medial half of the flexor digitorum profundus that is innervated by the ulnar nerve (the rest are innervated by the median nerve).

Origin
  • Humeral head: medial epicondyle of the humerus (common flexor origin)
  • Ulnar head: olecranon of ulna
Insertion
  • Pisiform
  • Hook of hamate (via pisohamate ligament)
  • Base of 5th metacarpal (via pisometacarpal ligament)
Innervation
Ulnar nerve The ulnar nerve enters the anterior compartment of the forearm by passing thruogh the gap between the humeral and ulnar heads of the flexor carpi ulnaris.
Blood Supply
Ulnar artery
Antagonist
Extensor carpi radialis brevis muscle and extensor carpi radialis longus muscle
Action Flexion and adduction at the wrist joint