Origin: there are 3 plantar interossei arising from the base and medial plantar surface of the 3rd, 4th, and 5th metatarsal bones.
Insertion: medial side of the base of the 1st phalanx of the same toe and into the tendons of the Extensor digitorum longus.
Action: Flex the proximal and extend the distal phalanges and adducts toes toward the axis of 2nd toe.
Nerve Supply: Lateral plantar, S1, S2. (See Innerv. Musc. Lower Limb )
Synergist: Dorsal Interossei.