Extensor pollicis longus (Musculus extensor pollicis longus)
Educational content only — not medical advice.
Anatomy
Arising from the posterior ulna, its tendon wraps around Lister tubercle on the radius in the third compartment — this deflection gives the thumb its characteristic extension and bounds the snuffbox medially.
Origin & insertion
Middle third of the posterior ulnar surface and the interosseous membrane.
Action
Extends the thumb distal phalanx and radially deviates the wrist; full thumb re-extension depends on its pull.
Innervation
Radial nerve — posterior interosseous branch (C7–C8).
Clinical notes
Its closed rupture (thumb mallet) after wrist trauma is the classic thumb tendon injury; weakness after distal radius fractures is mistaken for splint impingement.
Related structures
Educational references
FAQ
What is the role of the Extensor pollicis longus?
Arising from the posterior ulna, its tendon wraps around Lister tubercle on the radius in the third compartment — this deflection gives the thumb its characteristic extension and bounds the snuffbox medially.
Why is the Extensor pollicis longus clinically important?
Its closed rupture (thumb mallet) after wrist trauma is the classic thumb tendon injury; weakness after distal radius fractures is mistaken for splint impingement.
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