Lower limb

Third dorsal interosseous of the foot

Musculus interosseus dorsalis pedis III

Origin

Adjacent sides of the third and fourth metatarsal bones (metatarsals III and IV)

Insertion

Lateral side of the base of the proximal phalanx of the third toe, via the extensor expansion

Function

Abduction of the third toe laterally, flexion at the MTP joint and extension at the IP joints

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 third toe at the MTP joint.

Palpation

Difficult to distinguish individually, but the dorsal interossei can be felt as a group 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 interossei function contributes to claw toe deformity.

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