Adductor hallucis muscle
Adductor hallucis is a two-headed, intrinsic muscle of the sole of the foot. Among the three vertical groups of plantar foot muscles (lateral, central and medial), adductor hallucis muscle functionally belongs to the medial group of plantar foot muscles. However, it is anatomically located within the central compartment of foot.
Foot muscles are also divided horizontally into four layers from superficial to deep. In that classification, adductor hallucis comprises the third layer of plantar foot muscles, together with the flexor hallucis brevis and flexor digiti minimi brevis.
The function of adductor hallucis is to facilitate walking by adducting and flexing the great toe (hallux). It also contributes to maintaining the transverse and longitudinal arches of foot.
This article will discuss the anatomy and function of the adductor hallucis muscle.
Oblique head: bases of metatarsal bones 2-4, cuboid bone, lateral cuneiform bone, tendon of fibularis longus
Transverse head: plantar metatarsophalangeal ligaments of toes 3-5, deep transverse metatarsal ligaments of toes 3-5
|Insertion||Lateral aspect of base of proximal phalanx of great toe|
|Action||Metatarsophalangeal joint 1: Toe adduction, toe flexion; Support of longitudinal and transverse arches of foot|
|Innervation||Lateral plantar nerve (S2,S3)|
|Blood supply||Medial plantar artery, lateral plantar artery, plantar arch, plantar metatarsal arteries|
Origin and insertion
Adductor hallucis consists of the two heads; oblique and transverse. They have different origins, but share a common insertion.
The oblique head consists of lateral and medial parts. Both parts originate from the bases of metatarsal bones 2-4, cuboid, lateral cuneiform bones and tendon of fibularis longus. They both then course anteromedially, with the medial part blending with the tendon of flexor hallucis brevis on the lateral sesamoid bone of great toe. The lateral part meets with the tendon of the transverse head of adductor hallucis.
The transverse head originates as three bands from the plantar metatarsophalangeal ligaments of toes 3-5 and deep transverse metatarsal ligaments located between the respective toes. The bands course medially and fuse into a unique muscle belly which inserts together with the oblique head into the lateral surface of the base of proximal phalanx of great toe.
Note that the transverse head is quite variable; sometimes it might be absent, while in other situations it can attach to the first metatarsal bone and comprise the opponens hallucis muscle.
This muscle sits in the central compartment of the sole of the foot. It lies plantar (inferior) to the tendons of flexor digitorum longus, flexor digitorum brevis and plantar interossei muscles. Medially and proximally to the muscle is the flexor hallucis brevis.
The deep plantar arterial arch and deep branches of lateral plantar nerve course over the dorsal (superior) surface of the oblique head of adductor hallucis. In turn, the plantar metatarsal arteries pass over the dorsal surface of transverse head. The proper plantar digital nerves course over the plantar surfaces of both heads.
Adductor hallucis is innervated by the deep branch of lateral plantar nerve (S2, S3), which stems from the tibial nerve.
The main vascular source for this muscle is the posterior tibial artery with its branches;
- Deep branches of medial plantar artery
- Lateral plantar artery and its branches; deep plantar arch and plantar metatarsal arteries 1-4
Adductor hallucis muscle has two actions at the first metatarsophalangeal joint;
- It adducts the great toe, i.e. pulls it towards the foot’s midline.
- Together with flexor hallucis longus, it flexes the great toe.
These actions play important roles in the terminal stance phase of the gait cycle. By flexing and adducting the big toe, adductor hallucis reinforces the forefoot as the center of gravity for the body weight before the heel lifts up. In addition, due to the horizontal position of its transverse head, it stabilizes the foot arches and fixes the forefoot.
To expand your knowledge check out our learning materials about the muscles of the foot.