Dorsal interossei muscles of the foot

Origin and insertion

Dorsal interossei muscles are the two-headed muscles found between the metatarsal bones 1-5. The heads of each dorsal interossei originate from the opposing surfaces of metatarsal bones. The muscle fibers converge toward each other to give off a narrow tendon that continues its course towards the phalanges. 

The tendon of the first (most medial) dorsal interosseus muscle inserts onto the medial base of the second proximal phalanx, while the lateral three muscles insert onto the lateral bases of second to fourth proximal phalanges. Due to this inserting pattern, the second proximal phalanx is the only one with two dorsal interossei muscles (first and second) attached to its respective sides.

Relations

Dorsal interossei muscles run deep to the muscles of the third layer of the plantar muscles; flexor hallucis brevis, adductor hallucis and flexor digiti minimi brevis. 

Since the heads of dorsal interossei converge toward each other in an anteromedial fashion, they bound the angular spaces in the proximal parts of intermetatarsal intervals. These openings between the heads of second to fourth muscles serve as passageways for posterior perforating arteries on their way to the sole of foot, while the corresponding opening between the heads of the first dorsal interosseus muscle transmits the dorsalis pedis artery.

Innervation

Dorsal interossei muscles of the foot are innervated by lateral plantar nerve (S2-S3), which is a branch of the tibial nerve.

Blood supply

The vascularization of dorsal interossei muscles comes from several small arteries in the foot; 

• Anterior tibial artery, via dorsalis pedis and dorsal metatarsal arteries
• Posterior tibial artery, via lateral plantar and plantar metatarsal arteries

Functions

Although small, the dorsal interossei are strong muscles that in synergy with the plantar interossei flex the lateral three toes at the metatarsophalangeal joints. This action is important as it positions the toes in a way that flexor digitorum longus and brevis can perform their activity during jumping and running. 

Besides being involved in flexion, dorsal interossei also assist to the extensor digitorum longus and extensor digitorum brevis muscles in toe extension at the interphalangeal joints of second, third and fourth toes. Although it is of less importance, it is worth mentioning that these muscles also abduct the same three toes at metatarsophalangeal joints. Dorsal interossei muscles also contribute to the stability of the foot by supporting the anterior metatarsal, medial and lateral arches of the foot in running, walking and jumping.

To expand your knowledge check out our video about central muscles of the sole of foot, and then test your knowledge with our quiz about muscles of the foot.