Flexor digitorum profundus (Musculus flexor digitorum profundus)
Educational content only — not medical advice.
Anatomy
The deepest flexor layer on the ulnar aspect; its four tendons perforate superficialis to reach the distal phalanges. Its lateral half (index, middle) is median-innervated and medial half (ring, little) ulnar-innervated — the famous dual innervation.
Origin & insertion
Anteromedial surface of the proximal ulna and the interosseous membrane.
Action
Flexes the distal phalanges for the complete power grip, working in series with superficialis.
Innervation
Median nerve (radial half) and ulnar nerve (medial half) — C8–T1.
Clinical notes
Proximal ulnar injury abolishes distal flexion of ring and little fingers; the OK-sign test uses its dual innervation to assess the medial cord.
Related structures
Educational references
FAQ
What is the role of the Flexor digitorum profundus?
The deepest flexor layer on the ulnar aspect; its four tendons perforate superficialis to reach the distal phalanges. Its lateral half (index, middle) is median-innervated and medial half (ring, little) ulnar-innervated — the famous dual innervation.
Why is the Flexor digitorum profundus clinically important?
Proximal ulnar injury abolishes distal flexion of ring and little fingers; the OK-sign test uses its dual innervation to assess the medial cord.
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details