Flexor Hallucis Brevis
Foot · Lower Limb
The flexor hallucis brevis is a two-headed muscle of the third plantar layer lying against the first metatarsal. It arises from the plantar surfaces of the cuboid and lateral cuneiform and from the tendon of tibialis posterior, and it inserts by medial and lateral heads onto the corresponding sesamoid bones and the base of the proximal phalanx of the great toe. Its function is to flex the great toe at the metatarsophalangeal joint, an action important for the final push-off of gait. It is supplied by the medial plantar nerve (S1-S2). The two sesamoid bones embedded in its tendons protect the head of the first metatarsal and increase the muscle's leverage on the great toe.
Origin, Insertion, Action & Nerve
Origin
Plantar surfaces of the cuboid and lateral cuneiform and the tendon of tibialis posterior
Insertion
Medial and lateral sesamoids and base of the proximal phalanx of the great toe (medial and lateral heads)
Action
Flexes the great toe at the metatarsophalangeal joint
Nerve
Medial plantar nerve (S1–S2)
Attachments explained
The Flexor Hallucis Brevis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Plantar surfaces of the cuboid and lateral cuneiform and the tendon of tibialis posterior
Insertion
Medial and lateral sesamoids and base of the proximal phalanx of the great toe (medial and lateral heads)
Action & function
When the Flexor Hallucis Brevis contracts, it produces the following movement: Flexes the great toe at the metatarsophalangeal joint.
As part of the Foot group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Flexor Hallucis Brevis receives its nerve supply from the Medial plantar nerve (S1–S2). This nerve carries fibres from spinal segment(s) S1, S2.
Because a muscle can only contract when its nerve is intact, injury to the Medial plantar nerve or to its spinal roots (S1, S2) can weaken or paralyse the Flexor Hallucis Brevis, impairing the movements it normally produces (flexes the great toe at the metatarsophalangeal joint). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Flexor Hallucis Brevis (the OIANS method)
Study this muscle around its sesamoids. Its medial and lateral heads each carry a sesamoid bone as they cross the head of the first metatarsal to reach the base of the great toe's proximal phalanx. Picturing those sesamoids explains both why the muscle protects the metatarsal head and why it stops at the proximal phalanx, leaving distal flexion to the long flexor.
Contrast it with flexor hallucis longus to avoid confusion. The longus comes from the fibula and reaches the distal phalanx for powerful terminal flexion, while the brevis is intrinsic and flexes only the MTP joint. Its medial plantar nerve supply groups it with the other medial first-toe muscle, abductor hallucis, keeping the great-toe intrinsics organised.
Frequently asked questions
Where is the Flexor Hallucis Brevis located?
The Flexor Hallucis Brevis is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Flexor Hallucis Brevis?
Plantar surfaces of the cuboid and lateral cuneiform and the tendon of tibialis posterior
What is the insertion of the Flexor Hallucis Brevis?
Medial and lateral sesamoids and base of the proximal phalanx of the great toe (medial and lateral heads)
What movements does the Flexor Hallucis Brevis produce?
Flexes the great toe at the metatarsophalangeal joint
What nerve supplies the Flexor Hallucis Brevis?
Medial plantar nerve (S1–S2)
Is the Flexor Hallucis Brevis free to study in OIANS?
The Flexor Hallucis Brevis is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Flexor Hallucis Brevis
Test yourself on Lower Limb muscles with interactive quizzes and flashcards in the free OIANS app.
Quiz yourself → Flashcards Open the OIANS app
Browsing is always free. A one-time Lifetime unlock adds every region's quizzes, flashcards, progress tracking and explore tools.