Plantar interossei muscles

The plantar interossei muscles of the foot are three small, unipennate muscles located in the plantar aspect of the forefoot in the intermetatarsal spaces of the third, fourth, and fifth toes. Each muscle originates from the medial aspect of the bases and shafts of the third, fourth, and fifth metatarsal bones, respectively. Their fibers run distally and insert into the medial sides of the proximal phalanges and the extensor expansions of the same toes.

Functionally, the plantar interossei adduct the third, fourth, and fifth toes toward the second toe and assist in flexion at the metatarsophalangeal joints and extension at the interphalangeal joints. They are innervated by the lateral plantar nerve, a branch of the tibial nerve. Vascular supply is provided primarily by branches of the plantar metatarsal arteries, as demonstrated in detailed cadaveric studies.

Origin: Metatarsals

Insertion: Proximal phalanges

Nerve: lateral plantar nerve

Action: Adduct toes

Antagonist: Dorsal interossei of the foot

Gray's description: The Interossei in the foot are similar to those in the hand, with this exception, that they are grouped around the middle line of the second digit, instead of that of the third.They are seven in number, and consist of two groups, dorsal and plantar.

The Interossei plantares (Plantar interossei), three in number, lie beneath rather than between the metatarsal bones, and each is connected with but one metatarsal bone. They arise from the bases and medial sides of the bodies of the third, fourth, and fifth metatarsal bones, and are inserted into the medial sides of the bases of the first phalanges of the same toes, and into the aponeuroses of the tendons of the Extensor digitorum longus.