Dorsal interossei muscles of foot

At a glance

English

Dorsal interossei muscles of foot

Latin (TA2)

Musculi interossei dorsales pedis

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the dorsal interossei muscles of foot

The dorsal interossei occupy the spaces between the metatarsal bones, one muscle in each space, and form the deepest layer of the sole. They are seen best from the top of the foot, under the long and short extensor tendons. Each is bipennate: it springs by two heads from the facing sides of the neighbouring metatarsals, so its fibres slope in from both sides onto a central tendon.

Each tendon runs forwards beneath the deep transverse metatarsal ligament to the base of a proximal phalanx and into the extensor expansion over it, although the hoods of the toes are less developed than in the hand. The first reaches the inner side of the second toe; each of the others reaches the outer side of toes two, three and four in turn. The second toe therefore receives one on each side, which makes it the reference line of the foot, whereas in the hand that line passes through the middle finger. The great and little toes have their own abductors and receive none.

Their basic action is to spread the toes away from the second toe at the metatarsophalangeal joints, and to swing the second toe either way. Spreading is of little use in a shod foot. More important is their work with the plantar interossei: together they flex the metatarsophalangeal joints and hold the toes straight and steady, so that the long and short flexors can grip and push off without the toes buckling. They also help to support the transverse arch across the metatarsal heads.

The deep plantar artery, a branch of dorsalis pedis, dives into the sole between the first muscle's heads to join the plantar arch; between the heads of the others, perforating arteries pass up to the dorsum. All are supplied by the lateral plantar nerve, the fourth space by its superficial branch and the rest by its deep branch, with extra twigs to the first and second from the deep fibular nerve.

Attachments, action and supply

Origin

Two heads from the adjacent sides of the metatarsal bones bounding each space, mainly on their proximal halves.

Insertion

Proximal phalanx bases of toes two to four and their extensor expansions: the first on the inner side of toe two, the others on the outer sides of toes two to four.

Action

Abduct the toes from the line of the second toe; with the plantar interossei, flex the metatarsophalangeal joints and steady the toes; support the transverse arch.

Nerve supply

Lateral plantar nerve, deep and superficial branches (S2, S3); the first and second also receive twigs from the deep fibular nerve.

Blood supply

Arcuate artery, dorsal metatarsal arteries and plantar metatarsal arteries from the plantar arch.