Lower limb

First dorsal interosseous of the foot

Musculus interosseus dorsalis pedis I

Origin

Adjacent sides of the first and second metatarsal bones (metatarsal I and II)

Insertion

Medial side of the base of the proximal phalanx of the second toe, via the extensor expansion

Function

Abduction of the second toe (away from the axis through the second toe), flexion at the MTP joint and extension at the IP joints via the extensor expansion

Innervation

Lateral plantar nerve (branch of the tibial nerve), S2-S3

Movement & chain

Works together with the other dorsal and plantar interossei to spread and close the toes during the push-off phase of gait, and stabilizes the second toe at the MTP joint.

Palpation

Difficult to distinguish individually, but the dorsal interossei as a group can be felt in the intermetatarsal spaces on the dorsum of the foot during active toe spreading.

Clinical

In intrinsic foot muscle atrophy (for example due to polyneuropathy), loss of the interossei contributes to clawing of the toes.

Segmental innervation

S2–S3 (lateral plantar nerve)

In clinical practice

Diabetic foot inspection and pressure ulcer prevention; monitor for friction points from footwear or bedding and ensure correct anti-embolism stocking fit.

Region in the model

Lower limb