Flexor hallucis brevis is one of the muscles within the third layer on the plantar surface of the foot. It originates from the plantar surface of the:
- lateral cuneiform
- medial and intermediate cuneiforms in continuity with the tendinous insertion of tibialis posterior
Becoming muscular distally over the base of the first metatarsal, flexor hallucis brevis divides early into two tendons which insert distally into the base of the proximal phalanx of the big toe. Each tendon inserts via a sesamoid bone which provides protection from pressure arising from the head of the first metatarsal. The medial insertion is in continuity with the insertion of abductor hallucis. The lateral insertion is in continuity with adductor hallucis.
Flexor hallucis brevis is innervated by the medial plantar nerve (S2, S3).
Its action are to:
- flex the metatarsophalangeal joint of the big toe
- provide support to the medial longitudinal arch