Opponens Digiti Minimi (Foot)
Foot · Lower Limb
The opponens digiti minimi of the foot is an inconstant muscular slip on the lateral side of the sole, generally regarded as a deep part of the flexor digiti minimi brevis rather than a separate muscle. When present it arises from the long plantar ligament and the fibrous sheath of the fibularis longus tendon and inserts along the lateral border of the fifth metatarsal. Its action is to draw the fifth metatarsal plantarward and laterally, deepening the lateral part of the sole in a manner analogous to opposition in the hand. Like the neighbouring little-toe muscles, it is supplied by the superficial branch of the lateral plantar nerve (S2-S3). Because it is a variant, it is absent in many feet.
Origin, Insertion, Action & Nerve
Origin
Long plantar ligament and sheath of the fibularis longus tendon
Insertion
Lateral border of the fifth metatarsal
Action
Draws the fifth metatarsal plantarward and laterally (inconstant slip of flexor digiti minimi brevis)
Nerve
Superficial branch of the lateral plantar nerve (S2–S3)
Attachments explained
The Opponens Digiti Minimi (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
Long plantar ligament and sheath of the fibularis longus tendon
Insertion
Lateral border of the fifth metatarsal
Action & function
When the Opponens Digiti Minimi (Foot) contracts, it produces the following movement: Draws the fifth metatarsal plantarward and laterally (inconstant slip of flexor digiti minimi brevis).
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 Opponens Digiti Minimi (Foot) receives its nerve supply from the Superficial branch of 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 Superficial branch of the lateral plantar nerve or to its spinal roots (S2, S3) can weaken or paralyse the Opponens Digiti Minimi (Foot), impairing the movements it normally produces (draws the fifth metatarsal plantarward and laterally (inconstant slip of flexor digiti minimi brevis)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Opponens Digiti Minimi (Foot) (the OIANS method)
Treat this as a variant deep slip of flexor digiti minimi brevis, distinguished by its bony insertion on the fifth metatarsal rather than on a phalanx. That metatarsal attachment shifts its effect from flexing the toe to repositioning the metatarsal, which is why it borrows the name opponens by analogy with the hand.
Group it with the other lateral third-layer muscles by its origin from the long plantar ligament and fibularis longus sheath and its superficial lateral plantar nerve supply. When you encounter it, ask what a metatarsal insertion achieves that a phalangeal one cannot, and the answer, drawing the fifth metatarsal plantarward and laterally, marks it out from the standard little-toe flexor.
Frequently asked questions
Where is the Opponens Digiti Minimi (Foot) located?
The Opponens Digiti Minimi (Foot) is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Opponens Digiti Minimi (Foot)?
Long plantar ligament and sheath of the fibularis longus tendon
What is the insertion of the Opponens Digiti Minimi (Foot)?
Lateral border of the fifth metatarsal
What movements does the Opponens Digiti Minimi (Foot) produce?
Draws the fifth metatarsal plantarward and laterally (inconstant slip of flexor digiti minimi brevis)
What nerve supplies the Opponens Digiti Minimi (Foot)?
Superficial branch of the lateral plantar nerve (S2–S3)
Is the Opponens Digiti Minimi (Foot) free to study in OIANS?
The Opponens Digiti Minimi (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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