Abductor Ossis Metatarsi Quinti (Foot)
Foot · Lower Limb
The abductor ossis metatarsi quinti is an inconstant muscular slip on the lateral side of the foot, usually described as a variant portion of the abductor digiti minimi. When present it arises from the lateral process of the calcaneal tuberosity and inserts onto the tuberosity of the fifth metatarsal rather than onto a phalanx. Its action is to abduct the little toe and to help support the lateral longitudinal arch by steadying the base of the fifth metatarsal. Like the other lateral plantar muscles, it is supplied by the lateral plantar nerve (S2-S3). Because it is a variant, it is not found in every foot, and its size and presence differ considerably from one individual to another.
Origin, Insertion, Action & Nerve
Origin
Lateral process of the calcaneal tuberosity
Insertion
Tuberosity of the fifth metatarsal
Action
Abducts the fifth toe and supports the lateral longitudinal arch (inconstant variant slip)
Nerve
Lateral plantar nerve (S2–S3)
Attachments explained
The Abductor Ossis Metatarsi Quinti (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
Lateral process of the calcaneal tuberosity
Insertion
Tuberosity of the fifth metatarsal
Action & function
When the Abductor Ossis Metatarsi Quinti (Foot) contracts, it produces the following movement: Abducts the fifth toe and supports the lateral longitudinal arch (inconstant variant slip).
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 Abductor Ossis Metatarsi Quinti (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 Abductor Ossis Metatarsi Quinti (Foot), impairing the movements it normally produces (abducts the fifth toe and supports the lateral longitudinal arch (inconstant variant slip)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Abductor Ossis Metatarsi Quinti (Foot) (the OIANS method)
Treat this as a variant offshoot of the abductor digiti minimi rather than a separate textbook muscle. The key difference is its bony insertion onto the tuberosity of the fifth metatarsal instead of a phalanx, which shifts its emphasis from moving the toe toward steadying the lateral arch. Recognising it as an inconstant slip explains why it may be absent altogether.
Bundle it with the lateral plantar group by noting the shared origin from the lateral calcaneal process and the shared lateral plantar nerve supply. When you meet it, ask what its metatarsal insertion does that a phalangeal one cannot, and the answer, arch support at the fifth metatarsal base, distinguishes it cleanly from the standard abductor of the little toe.
Frequently asked questions
Where is the Abductor Ossis Metatarsi Quinti (Foot) located?
The Abductor Ossis Metatarsi Quinti (Foot) is a muscle of the Foot group, located in the Lower Limb.
What is the origin of the Abductor Ossis Metatarsi Quinti (Foot)?
Lateral process of the calcaneal tuberosity
What is the insertion of the Abductor Ossis Metatarsi Quinti (Foot)?
Tuberosity of the fifth metatarsal
What movements does the Abductor Ossis Metatarsi Quinti (Foot) produce?
Abducts the fifth toe and supports the lateral longitudinal arch (inconstant variant slip)
What nerve supplies the Abductor Ossis Metatarsi Quinti (Foot)?
Lateral plantar nerve (S2–S3)
Is the Abductor Ossis Metatarsi Quinti (Foot) free to study in OIANS?
The Abductor Ossis Metatarsi Quinti (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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