The flexor digitorum profundus is one of three muscles in the deep compartment of the anterior muscles of the forearm.

The two other muscles are the flexor pollicis longus and the pronator quadratus.

Origin

Upper 3/4 of the anterior and medial surfaces of the body of the ulna, interosseous membrane and deep fascia of the forearm

Insertion

Palmar surfaces of the distal phalanges of the index, middle, ring and little fingers.

 

Four tendons are formed within the distal forearm, which pass through the carpal tunnel along with the tendons of its counterpart muscle, the flexor digitorum superficialis (also 4 tendons), the flexor pollicis longus and the median nerve.

The tendons of the flexor digitorum superficialis split to insert onto the margins of the base of the middle phalanges, allowing the deeper tendons of the flexor digitorum profundus to pass through and inserting more distally on the bases of the distal phalanges. This can be remembered with the mnemonic superficialis splits, profundus passes through.

The tendons of the flexor digitorum profundus within the palm of the hand provide the origin for the lumbrical muscles, which arise from the sides of these tendons.

Innervation
  • Lateral half: anterior interosseus nerve (from median nerve)
  • Medial half: ulnar nerve
Blood Supply

Anterior interosseus artery

Antagonist

Extensor digitorum

Action

The flexor digitorum profundus produces flexion at the following joints:

  • Distal interphalangeal joints: flexes digits 2-5
  • Proximal interphalangeal joints: flexes digits 2-5
  • Metacarpophalangeal joints (2-5)
  • Wrist

Tip: think of the joints that the tendons traverse!