Fourth Dorsal Interosseous (Foot)
Foot · Lower Limb
The fourth dorsal interosseous of the foot is the most lateral of the four bipennate dorsal interossei, occupying the space between the fourth and fifth metatarsals and arising from their adjacent sides. It inserts on the lateral side of the proximal phalanx of the fourth toe and thus abducts that toe, pulling it laterally away from the second-toe axis. Like its companions, it also flexes the metatarsophalangeal joint and extends the interphalangeal joints of its toe through the dorsal digital expansion. It is supplied by the lateral plantar nerve (S2, S3). By spreading the fourth toe and steadying the lateral forefoot, it works with the abductor digiti minimi to support the outer border of the foot.
Origin, Insertion, Action & Nerve
Origin
Adjacent sides of the 4th and 5th metatarsals (bipennate)
Insertion
Lateral side of proximal phalanx of the 4th toe
Action
Abducts the 4th toe from the 2nd-toe axis; flexes MTP and extends IP joints
Nerve
Lateral plantar nerve (S2, S3); first and second also receive the deep fibular nerve
Attachments explained
The Fourth 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 4th and 5th metatarsals (bipennate)
Insertion
Lateral side of proximal phalanx of the 4th toe
Action & function
When the Fourth Dorsal Interosseous (Foot) contracts, it produces the following movements: Abducts the 4th toe from the 2nd-toe axis; 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 Fourth 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 Fourth Dorsal Interosseous (Foot), impairing the movements it normally produces (abducts the 4th toe from the 2nd-toe axis). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Fourth Dorsal Interosseous (Foot) (the OIANS method)
Fix this as the outermost dorsal interosseous acting on the fourth toe. Its lateral insertion means it spreads that toe toward the little toe, and grouping it with the abductor digiti minimi, which lies just beyond it on the lateral border, gives you a mental map of the muscles that widen the outer forefoot.
Confirm the simplified supply: like the third, the fourth dorsal interosseous receives only the lateral plantar nerve, with no deep fibular twig. Holding all four dorsal interossei together, remember that they all abduct from the second-toe axis and that only the medial two carry the extra dorsal nerve, which turns four seemingly identical muscles into a short, ordered list.
Frequently asked questions
Where is the Fourth Dorsal Interosseous (Foot) located?
The Fourth Dorsal Interosseous (Foot) is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Fourth Dorsal Interosseous (Foot)?
Adjacent sides of the 4th and 5th metatarsals (bipennate)
What is the insertion of the Fourth Dorsal Interosseous (Foot)?
Lateral side of proximal phalanx of the 4th toe
What movements does the Fourth Dorsal Interosseous (Foot) produce?
Abducts the 4th toe from the 2nd-toe axis; flexes MTP and extends IP joints
What nerve supplies the Fourth Dorsal Interosseous (Foot)?
Lateral plantar nerve (S2, S3); first and second also receive the deep fibular nerve
Is the Fourth Dorsal Interosseous (Foot) free to study in OIANS?
The Fourth 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
Study the Fourth Dorsal Interosseous (Foot)
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.