Second Lumbrical (Foot)
Foot · Lower Limb
The second lumbrical of the foot is a small bipennate muscle of the second plantar layer, arising from the adjacent sides of the flexor digitorum longus tendons passing to the second and third toes. It inserts on the medial side of the extensor expansion of the third toe. Acting on that toe, it flexes the metatarsophalangeal joint while extending the interphalangeal joints, pressing the toe pad toward the ground. It is supplied by the lateral plantar nerve (S2, S3), unlike the first lumbrical which takes the medial plantar nerve. Together the lumbricals keep the toes from buckling as the long flexors contract, contributing to a smooth, balanced push-off.
Origin, Insertion, Action & Nerve
Origin
Adjacent sides of the flexor digitorum longus tendons to the 2nd and 3rd toes
Insertion
Medial side of the extensor expansion of the 3rd toe
Action
Flexes the MTP joint and extends the IP joints of the 3rd toe
Nerve
Lateral plantar nerve (S2, S3)
Attachments explained
The Second Lumbrical (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 flexor digitorum longus tendons to the 2nd and 3rd toes
Insertion
Medial side of the extensor expansion of the 3rd toe
Action & function
When the Second Lumbrical (Foot) contracts, it produces the following movement: Flexes the MTP joint and extends the IP joints of the 3rd toe.
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 Second Lumbrical (Foot) receives its nerve supply from the Lateral plantar nerve (S2, S3). 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 Second Lumbrical (Foot), impairing the movements it normally produces (flexes the MTP joint and extends the IP joints of the 3rd toe). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Second Lumbrical (Foot) (the OIANS method)
Learn the second lumbrical as the first of the bipennate three. Whereas the first lumbrical clings to just one tendon, the second through fourth each sit between two long flexor tendons, drawing origin from both. Its target is the third toe, one digit lateral to its origin toes, so applying the flex-MTP, extend-IP rule to the third toe fixes its action.
Bracket it with the lateral plantar nerve group. From the second lumbrical onward, all are supplied by the lateral plantar nerve, so the switch from medial to lateral supply happens between the first and second lumbricals. Remembering that boundary is the single most reliable way to place lumbrical innervation on an exam.
Frequently asked questions
Where is the Second Lumbrical (Foot) located?
The Second Lumbrical (Foot) is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Second Lumbrical (Foot)?
Adjacent sides of the flexor digitorum longus tendons to the 2nd and 3rd toes
What is the insertion of the Second Lumbrical (Foot)?
Medial side of the extensor expansion of the 3rd toe
What movements does the Second Lumbrical (Foot) produce?
Flexes the MTP joint and extends the IP joints of the 3rd toe
What nerve supplies the Second Lumbrical (Foot)?
Lateral plantar nerve (S2, S3)
Is the Second Lumbrical (Foot) free to study in OIANS?
The Second Lumbrical (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 Second Lumbrical (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.