Corpus: Adductor hallucis muscle
Synonym: big toe adductor
1. Definition
2. Structure
2.1. Origin
The adductor hallucis muscle comprises two muscle heads with distinct origins: the transverse head and the oblique head.
2.2. Transverse Head
The transverse head is a narrow, flat muscle head that originates from the ligamentous structures or joint capsules of the 3rd, 4th, and 5th metatarsophalangeal joints, as well as the metatarsal transversus profundum ligament. It runs almost perpendicular to the metatarsal bones.
2.3. Oblique head
The oblique head is a broad, fleshy muscle head that runs diagonally across the foot, contributing to the arch. It originates at the base of the 2nd and 3rd (and sometimes 4th) metatarsal bones, and the tendon sheath of the fibularis longus muscle. Additional fibers originate from the cuboid bone, the lateral cuneiform bone, the long plantar ligament, and the calcaneocuboid plantar ligament.
2.4. Attachment
Both muscle heads merge to form a common tendon, which, along with the lateral head of the flexor hallucis brevis muscle, attaches to the lateral side of the base of the proximal phalanx of the big toe and the adjacent lateral sesamoid bone.
3. Innervation
The adductor hallucis muscle is innervated by the lateral plantar nerve, a branch of the tibial nerve.
4. Function
As its name indicates, the adductor hallucis muscle primarily functions to adduct the big toe at the metatarsophalangeal joint. Additionally, it supports the transverse arch of the foot by maintaining transverse tension.