First Dorsal Interosseous (Foot)
Foot · Lower Limb
The first dorsal interosseous of the foot is a bipennate muscle occupying the space between the first and second metatarsals. Like all four dorsal interossei, it arises from the adjacent sides of two neighbouring metatarsals, here the first and second, and inserts onto the medial side of the proximal phalanx of the second toe. Because toe abduction is defined relative to the axis of the second toe, this muscle pulls the second toe medially, and together with the interossei it also flexes the metatarsophalangeal joint while extending the interphalangeal joints through the dorsal expansion. It is supplied by the lateral plantar nerve (S2, S3), though the first and second dorsal interossei also receive a twig from the deep fibular nerve. Its accessible position between the first two metatarsals makes it the interosseous most often identified on the dorsum of the foot.
Origin, Insertion, Action & Nerve
Origin
Adjacent sides of the 1st and 2nd metatarsals (bipennate)
Insertion
Medial side of proximal phalanx of the 2nd toe
Action
Abducts the 2nd toe medially (from the axis of the 2nd toe); flexes MTP and extends IP joints
Nerve
Lateral plantar nerve (S2, S3); first and second also receive the deep fibular nerve
Attachments explained
The First Dorsal Interosseous (Foot) 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
Adjacent sides of the 1st and 2nd metatarsals (bipennate)
Insertion
Medial side of proximal phalanx of the 2nd toe
Action & function
When the First Dorsal Interosseous (Foot) contracts, it produces the following movements: Abducts the 2nd toe medially (from the axis of the 2nd toe); flexes MTP and extends IP 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 First Dorsal Interosseous (Foot) receives its nerve supply from the Lateral plantar nerve (S2, S3); first and second also receive the deep fibular nerve. This nerve carries fibres from spinal segment(s) S2, S3.
Because a muscle can only contract when its nerve is intact, injury to the Lateral plantar nerve or to its spinal roots (S2, S3) can weaken or paralyse the First Dorsal Interosseous (Foot), impairing the movements it normally produces (abducts the 2nd toe medially (from the axis of the 2nd toe)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the First Dorsal Interosseous (Foot) (the OIANS method)
Anchor the reference axis first: in the foot, abduction and adduction are measured from the second toe, not the middle digit as in the hand. The first dorsal interosseous inserts on the medial side of the second toe, so it pulls that toe toward the midline of the body but medially away from the second-toe axis, which is why it counts as an abductor. Fix the axis idea once and every foot interosseous becomes predictable.
Use the dual nerve supply as a distinguishing hook. Although the lateral plantar nerve supplies the interossei as a group, the first and second dorsal interossei uniquely also receive the deep fibular nerve on the dorsum. Pairing that fact with its bipennate origin from the first and second metatarsals separates this muscle clearly from the more laterally placed dorsal interossei.
Frequently asked questions
Where is the First Dorsal Interosseous (Foot) located?
The First Dorsal Interosseous (Foot) is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the First Dorsal Interosseous (Foot)?
Adjacent sides of the 1st and 2nd metatarsals (bipennate)
What is the insertion of the First Dorsal Interosseous (Foot)?
Medial side of proximal phalanx of the 2nd toe
What movements does the First Dorsal Interosseous (Foot) produce?
Abducts the 2nd toe medially (from the axis of the 2nd toe); flexes MTP and extends IP joints
What nerve supplies the First Dorsal Interosseous (Foot)?
Lateral plantar nerve (S2, S3); first and second also receive the deep fibular nerve
Is the First Dorsal Interosseous (Foot) free to study in OIANS?
The First Dorsal Interosseous (Foot) 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
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