First Lumbrical of Foot (Musculus lumbricalis pedis primus)
Educational content only — not medical advice.
Anatomy
The single-headed first of the four small vermiform muscles of the sole. It arises from the medial surface of the first tendon of flexor digitorum longus — the only unipennate one — and passes on the medial side of the second toe to reach the extensor hood. It has no bony attachment at either end, a defining feature of the lumbricals.
Origin & insertion
From the medial surface of the first tendon of flexor digitorum longus, into the medial aspect of the extensor hood and metatarsophalangeal capsule of the second toe.
Action
Flexes the metatarsophalangeal joint of the second toe and extends its interphalangeal joints through the hood.
Innervation
Medial plantar nerve (S1–S2).
Clinical notes
The lumbricals counter the long flexors at the metatarsophalangeal joints; their failure in the intrinsic-minus (claw) foot lets the toes buckle into clawing at push-off. The first lumbrical is spared longest in Charcot-Marie-Tooth disease because of its medial plantar supply.
Related structures
Educational references
FAQ
What is the role of the First Lumbrical of Foot?
The single-headed first of the four small vermiform muscles of the sole. It arises from the medial surface of the first tendon of flexor digitorum longus — the only unipennate one — and passes on the medial side of the second toe to reach the extensor hood. It has no bony attachment at either end, a defining feature of the lumbricals.
Why is the First Lumbrical of Foot clinically important?
The lumbricals counter the long flexors at the metatarsophalangeal joints; their failure in the intrinsic-minus (claw) foot lets the toes buckle into clawing at push-off. The first lumbrical is spared longest in Charcot-Marie-Tooth disease because of its medial plantar supply.
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details