(plan'tahr in-tĕr-os'ē-ŭs mŭs'ĕl) Three intrinsic muscles of foot; origin, the medial side of the third, fourth, and fifth metatarsal bones; insertion, corresponding side of proximal phalanx of the same toes; action, adducts three lateral toes; nerve supply, lateral plantar. Synonym(s): musculus interosseus plantaris [TA] .