Third dorsal interosseous muscle

The dorsal interossei muscles of the foot are four bipennate intrinsic muscles located in the intermetatarsal spaces. Each muscle arises by two heads from the adjacent sides of the metatarsal bones and occupies the dorsal aspect of the foot. The muscles insert into the bases of the proximal phalanges and the extensor expansion of the second, third, and fourth toes. Functionally, they abduct the toes away from the second digit, which serves as the axis of abduction/adduction in the foot. Vascular supply is primarily from the dorsal metatarsal arteries, which course close to the metatarsal bones and provide segmental branches to both faces of the interosseous muscles.

Nerve: Plantar nerve

Action: Abduct toes

Antagonist: Plantar interossei muscles

Gray's Description: The Interossei dorsales (Dorsal interossei), four in number, are situated between the metatarsal bones. They are bipenniform muscles, each arising by two heads from the adjacent sides of the metatarsal bones between which it is placed; their tendons areinserted into the bases of the first phalanges, and into the aponeurosis of the tendons of the Extensor digitorum longus. In the angular interval left between the heads of each of the three lateral muscles, one of the perforating arteries passes to the dorsum of the foot; through the space between the heads of the first muscle the deep plantar branch of the dorsalis pedis artery enters the sole of the foot. The first is inserted into the medial side of the second toe; the other three are inserted into the lateral sides of the second, third, and fourth toes.