Second Plantar Interosseous (Foot)
Foot · Lower Limb
The second plantar interosseous is a unipennate muscle deep in the sole, arising from the medial side and base of the fourth metatarsal and inserting on the medial side of the proximal phalanx of the fourth toe. It adducts the fourth toe, drawing it medially toward the second-toe axis, and like the other interossei it flexes the metatarsophalangeal joint and extends the interphalangeal joints of that toe. It is supplied by the lateral plantar nerve (S2, S3). Working with the first and third plantar interossei, it pulls toes three, four, and five toward the midline of the foot, complementing the spreading action of the dorsal interossei.
Origin, Insertion, Action & Nerve
Origin
Medial side and base of the 4th metatarsal (unipennate)
Insertion
Medial side of proximal phalanx of the 4th toe
Action
Adducts the 4th toe toward the 2nd-toe axis; flexes MTP and extends IP joints
Nerve
Lateral plantar nerve (S2, S3)
Attachments explained
The Second Plantar 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
Medial side and base of the 4th metatarsal (unipennate)
Insertion
Medial side of proximal phalanx of the 4th toe
Action & function
When the Second Plantar Interosseous (Foot) contracts, it produces the following movements: Adducts the 4th toe toward 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 Second Plantar Interosseous (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 Plantar Interosseous (Foot), impairing the movements it normally produces (adducts the 4th toe toward the 2nd-toe axis). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Second Plantar Interosseous (Foot) (the OIANS method)
Learn this muscle as the middle plantar adductor acting on the fourth toe. Its single-metatarsal origin from the fourth ray and medial insertion on the fourth toe mean it pulls that toe toward the second-toe axis, the definition of adduction here. Keeping the PAD rule in mind confirms its function without memorising it separately.
Anchor the whole plantar interosseous set together: there are three, serving toes three, four, and five, each pulling medially toward the second toe. The second plantar interosseous is the fourth-toe member, all supplied by the lateral plantar nerve, so once you fix the toe list you have located every plantar interosseous at once.
Frequently asked questions
Where is the Second Plantar Interosseous (Foot) located?
The Second Plantar Interosseous (Foot) is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Second Plantar Interosseous (Foot)?
Medial side and base of the 4th metatarsal (unipennate)
What is the insertion of the Second Plantar Interosseous (Foot)?
Medial side of proximal phalanx of the 4th toe
What movements does the Second Plantar Interosseous (Foot) produce?
Adducts the 4th toe toward the 2nd-toe axis; flexes MTP and extends IP joints
What nerve supplies the Second Plantar Interosseous (Foot)?
Lateral plantar nerve (S2, S3)
Is the Second Plantar Interosseous (Foot) free to study in OIANS?
The Second Plantar 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 Second Plantar Interosseous (Foot)
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