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Flexor Digitorum Profundus Muscle Anatomy

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Origin
  • Upper three-fourths of the anterior and medial surfaces of the ulna
  • Interosseous membrane
Insertion
  • Palmar surface of the distal phalanges of digits 2-5
Action
  • Flexes the metacarpophalangeal and interphalangeal joints of digits 2-5
  • Weak assistance in wrist flexion
Innervation
  • Lateral part (digits 2-3): Anterior interosseous branch of the median nerve (C8-T1)
  • Medial part (digits 4-5): Ulnar nerve (C8, T1)
Blood Supply
  • Anterior interosseous artery
Last updated: Estimated Reading Time: 6 min

Location & Overview

The flexor digitorum profundus is located deep to the flexor digitorum superficialis. The flexor digitorum profundus passes through a split in the flexor digitorum superficialis’ distal tendon. This split is located just before the proximal interphalangeal joint. The proximal interphalangeal joint is located between the middle and proximal phalanges of the finger, as shown in the images below. The flexor digitorum profundus is the only muscle that can flex the distal interphalangeal joints of the fingers; these are the joints located at the tips of the fingers. The flexor digitorum profundus passes deep to the flexor retinaculum within the common flexor sheath (i.e. it passes through the carpal tunnel). The carpal tunnel is a narrow passageway formed by the bones and ligaments of the wrist joint. The flexor retinaculum forms the anterior ‘roof’ of the carpal tunnel.[1,2]

Flexor digitorum profundus from an anterior and medial view
Here, we can see the flexor digitorum profundus from an anterior and medial view.
Flexor digitorum profundus distal tendon
Here, we can see a closer look at the flexor digitorum profundus’ distal tendon.
Image of the flexor digitorum profundus from a superficial view.
Highlighted in green, we can see the flexor digitorum profundus from a superficial view. We can see how it passes through a split in the flexor digitorum superficialis at its distal end.
A labeled diagram of the bones and the joints of the phalanges of the hand.
Here, we can see a labeled diagram of the bones and joints of the phalanges of the hand.

Origin & Insertion

The flexor digitorum profundus originates from the upper three-fourths of the anterior and medial surfaces of the ulna and from the interosseous membrane. It then continues distally down the forearm, crossing the wrist joint via the carpal tunnel, and finally connects to the tips of the fingers (distal phalanges). It inserts onto the bases of the distal phalanges of the 2nd, 3rd, 4th, and 5th digits.[1,2]

Origin point of the flexor digitorum profundus muscle highlighted in red on the skeleton.
Here, we can see the first origin point of the flexor digitorum profundus muscle highlighted in red. The origin is on the upper three-fourths of the anterior and medial surfaces of the ulna.
The origin point of the flexor digitorum profundus on the interosseous membrane.
Here, we can see the second origin point of the flexor digitorum profundus muscle highlighted in red on the interosseous membrane.
The insertion points of the flexor digitorum profundus muscle marked in blue on the skeleton.
Here, we can see the insertion points of the flexor digitorum profundus muscle highlighted in blue. The insertions are on the palmar surfaces of the distal phalanges of digits 2-5.

Action & Function

The flexor digitorum profundus enables flexion of several joints in the fingers. It can flex the metacarpophalangeal and interphalangeal joints of the index, middle, ring, and little fingers. Additionally, it can assist with wrist flexion at the midcarpal joint. The muscle’s medial part flexes the little and ring fingers (digits 4 and 5), while its lateral part flexes the index and middle fingers (digits 2 and 3).[1,2] To view a labeled diagram of the bones and joints of the phalanges of the hand, see the image located at the end of the ‘Location & Overview’ section, or select here to go straight to it.

Image of a hand demonstrating the movement of finger flexion.
This image demonstrates finger flexion, which is the action of bending the fingers toward the palm of the hand. The left side of the image depicts flexion happening at the metacarpophalangeal joint, while the right side shows finger flexion occurring at the interphalangeal joints (specifically the proximal and distal interphalangeal joints). Flexion at all three of these joints is an action of the flexor digitorum profundus.
Image shows an arm demonstrating the movement of wrist flexion.
This image shows wrist flexion, which is the movement of bending the wrist toward the underside of the forearm (anterior surface of the forearm). The opposite of wrist flexion is wrist extension, which involves extending the wrist toward the top of the forearm (posterior surface of the forearm). The flexor digitorum profundus muscle can provide weak assistance during wrist flexion.

Innervation

The lateral part of the flexor digitorum profundus is innervated by the anterior interosseous nerve, which is a branch of the median nerve. The lateral part acts on the index and middle fingers. The medial part of the flexor digitorum profundus is innervated by the ulnar nerve. The medial part acts on the ring and little fingers.[1,2]

anterior interosseous nerve and median nerve
Here, we can see the anterior interosseous nerve, which is a branch of the median nerve. The median nerve is highlighted in red on the right-hand side.

Blood Supply

Blood is supplied to the flexor digitorum profundus via the anterior interosseous artery. The anterior interosseous artery is a branch of the common interosseous artery.[2]

References

  1. [1] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017
  2. [2] Lung BE, Burns B. Anatomy, Shoulder and Upper Limb, Hand Flexor Digitorum Profundus Muscle. (Updated 2021 Oct 30). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526046/

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