Flexor Digitorum Brevis
Foot · Lower Limb
The flexor digitorum brevis is the central muscle of the first plantar layer, lying directly deep to the plantar aponeurosis in the middle of the sole. It arises from the medial process of the calcaneal tuberosity and the plantar aponeurosis, and it divides into four tendons that split to insert on the sides of the middle phalanges of the second to fifth toes. Its action is to flex those toes at the proximal interphalangeal joints and, with continued contraction, at the metatarsophalangeal joints, helping to grip the ground during gait. It is supplied by the medial plantar nerve (S1-S2). Its tendons are perforated by those of flexor digitorum longus, echoing the arrangement of flexor digitorum superficialis and profundus in the hand.
Origin, Insertion, Action & Nerve
Origin
Medial process of the calcaneal tuberosity and plantar aponeurosis
Insertion
Sides of the middle phalanges of toes 2–5
Action
Flexes toes 2–5 at the proximal interphalangeal and metatarsophalangeal joints
Nerve
Medial plantar nerve (S1–S2)
Attachments explained
The Flexor Digitorum 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
Medial process of the calcaneal tuberosity and plantar aponeurosis
Insertion
Sides of the middle phalanges of toes 2–5
Action & function
When the Flexor Digitorum Brevis contracts, it produces the following movement: Flexes toes 2–5 at the proximal interphalangeal and metatarsophalangeal joints.
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 Digitorum 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 Digitorum Brevis, impairing the movements it normally produces (flexes toes 2–5 at the proximal interphalangeal and metatarsophalangeal joints). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Flexor Digitorum Brevis (the OIANS method)
Study this muscle as the foot's version of flexor digitorum superficialis. Each of its tendons splits to insert on the sides of a middle phalanx and is pierced by the deeper long flexor tendon, so its action is flexion of toes 2-5 at the proximal interphalangeal joints, exactly the superficial layer's role in the hand.
Use its central position and medial plantar nerve supply to anchor the first plantar layer as a trio: abductor hallucis medially, flexor digitorum brevis in the middle, and abductor digiti minimi laterally. Remembering that the middle and medial members share the medial plantar nerve while the lateral one takes the lateral plantar nerve keeps the layer's innervation straight.
Frequently asked questions
Where is the Flexor Digitorum Brevis located?
The Flexor Digitorum Brevis is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Flexor Digitorum Brevis?
Medial process of the calcaneal tuberosity and plantar aponeurosis
What is the insertion of the Flexor Digitorum Brevis?
Sides of the middle phalanges of toes 2–5
What movements does the Flexor Digitorum Brevis produce?
Flexes toes 2–5 at the proximal interphalangeal and metatarsophalangeal joints
What nerve supplies the Flexor Digitorum Brevis?
Medial plantar nerve (S1–S2)
Is the Flexor Digitorum Brevis free to study in OIANS?
The Flexor Digitorum 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 Digitorum 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.