Flexor pollicis brevis

Hands

Origin: Flexor retinaculum and trapezium
Insertion: Thumb side of the base of the proximal phalanx of the thumb
Action: Flexes the thumb at its base joint
Nerve supply: Recurrent branch of the median nerve (superficial head) and deep branch of the ulnar nerve (deep head, C8–T1)

A muscle of the ball of the thumb, beside the abductor pollicis brevis. It bends the thumb at its base and helps bring it across the palm.

Exercises that train the flexor pollicis brevis

No exercise in this guide targets the flexor pollicis brevis directly yet.

Last updated 18 October 2026. For education only — not medical advice, and not reviewed by a clinician.