Extensor Digitorum Longus
Leg · Lower Limb
The extensor digitorum longus is a pennate muscle of the anterior compartment of the leg lying lateral to the tibialis anterior. It arises from the lateral condyle of the tibia, the anterior surface of the fibula, and the interosseous membrane, and its tendon divides into four slips that pass onto the dorsum of the foot to insert, through extensor expansions, onto the middle and distal phalanges of the lateral four toes. It extends the lateral four toes at the metatarsophalangeal and interphalangeal joints and, because its tendons cross the front of the ankle, it also assists dorsiflexion of the ankle. It is supplied by the deep fibular (peroneal) nerve (L5, S1). Its four tendons fan out visibly across the dorsum of the foot when the toes are lifted.
Origin, Insertion, Action & Nerve
Origin
Lateral condyle of tibia, anterior surface of fibula, interosseous membrane
Insertion
Middle and distal phalanges of lateral four toes (digits 2-5) (via extensor expansions)
Action
Extension of lateral four toes (digits 2-5); dorsiflexion of ankle
Nerve
Deep fibular (peroneal) nerve (L5, S1)
Attachments explained
The Extensor Digitorum Longus 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
Lateral condyle of tibia, anterior surface of fibula, interosseous membrane
Insertion
Middle and distal phalanges of lateral four toes (digits 2-5) (via extensor expansions)
Action & function
When the Extensor Digitorum Longus contracts, it produces the following movements: Extension of lateral four toes (digits 2-5); dorsiflexion of ankle.
As part of the Leg 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 Extensor Digitorum Longus receives its nerve supply from the Deep fibular (peroneal) nerve (L5, S1). This nerve carries fibres from spinal segment(s) L5, S1.
Because a muscle can only contract when its nerve is intact, injury to the Deep fibular or to its spinal roots (L5, S1) can weaken or paralyse the Extensor Digitorum Longus, impairing the movements it normally produces (extension of lateral four toes (digits 2-5)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Extensor Digitorum Longus (the OIANS method)
Group the extensor digitorum longus with the other anterior compartment muscles as dorsiflexors, but distinguish it by its four tendons spreading to toes two through five. Watching those tendons rise on the back of the foot when you lift your toes makes both its digit-extending and ankle-dorsiflexing roles obvious, since the tendons must pass in front of the ankle to reach the toes.
Remember that it inserts through extensor expansions, the same hood arrangement seen in the hand, which lets it extend both the metatarsophalangeal and interphalangeal joints. Keep it paired with extensor digitorum brevis, the short muscle on the dorsum of the foot that reinforces this action for toes two to four, and with its shared deep fibular nerve (L5, S1) supply so the anterior compartment stays a single unit in memory.
Frequently asked questions
Where is the Extensor Digitorum Longus located?
The Extensor Digitorum Longus is a muscle of the Leg group, located in the Lower Limb.
What is the origin of the Extensor Digitorum Longus?
Lateral condyle of tibia, anterior surface of fibula, interosseous membrane
What is the insertion of the Extensor Digitorum Longus?
Middle and distal phalanges of lateral four toes (digits 2-5) (via extensor expansions)
What movements does the Extensor Digitorum Longus produce?
Extension of lateral four toes (digits 2-5); dorsiflexion of ankle
What nerve supplies the Extensor Digitorum Longus?
Deep fibular (peroneal) nerve (L5, S1)
Is the Extensor Digitorum Longus free to study in OIANS?
The Extensor Digitorum Longus 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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