MuscleForearm — anterior (deep)
Flexor pollicis longus
Latin: M. flexor pollicis longus
Location: Forearm
View the flexor pollicis longus in 3DOrigin
Anterior surface of the radius and interosseous membrane.
Insertion
Base of the distal phalanx of the thumb.
Action
Flexes the thumb's interphalangeal joint — precision pinch and grip.
Nerve supply
Anterior interosseous nerve (median, C8–T1).
Blood supply
Anterior interosseous artery.
Clinical relevance
Its synovial sheath forms the radial bursa, which can communicate with the ulnar bursa (horseshoe abscess); anterior interosseous nerve palsy abolishes thumb IP flexion (the weak 'OK' sign).
Educational anatomy reference, not medical advice. About this content.