Abductor hallucis muscle

Origin and insertion

Abductor hallucis is a small and slender, but powerful muscle that has three origin points and one insertion. It originates from the medial process of the calcaneal tuberosity, plantar aponeurosis and the superficial layer of flexor retinaculum.

From here, the muscle fibers run anteriorly and medially, forming a tendon at the level of the body of first metatarsal bone. The tendon courses along the medial border of first metatarsophalangeal joint to finally insert to the base of proximal phalanx of great toe.

Relations

Abductor hallucis muscle is the most medial muscle of the foot, running medally to flexor hallucis brevis muscle. The plantar surface of the muscle is covered by the plantar aponeurosis, while its dorsal surface is related to the tendon of flexor digitorum longus, medial plantar artery and nerve. The originating fibers of abductor hallucis and calcaneus build a space called porta pedis. This space serves as a tunnel through which lateral and medial plantar nerves and vessels pass. 

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Innervation

Abductor hallucis muscle is innervated by the medial plantar nerve (root value S1 - S3), the larger of the two terminal branches of the tibial nerve.

Blood supply

The blood supply for abductor hallucis muscle comes from two arteries; 

• Medial plantar artery, a branch of posterior tibial artery 
• First plantar metatarsal artery, a branch of lateral plantar artery

Function

As the name of this muscle indicates, its main action is the abduction of the big toe at the first metatarsophalangeal joint. This action preserves the central position of the big toe during walking, and if it’s hindered it may result in deformities of the toes such is hallux valgus.

Together with flexor hallucis longus and flexor hallucis brevis muscles, abductor hallucis aids the flexion of the big toe. The muscle also helps in maintaining the medial longitudinal arch of the foot while walking. 

To expand your knowledge check out our learning materials about the muscles of the foot.