Second lumbrical muscle

The lumbrical muscles of the foot are four small, intrinsic muscles located in the central compartment of the sole. They originate from the tendons of the flexor digitorum longus (FDL). Each lumbrical muscle courses distally along the medial side of the corresponding toe, passing plantar to the deep transverse metatarsal ligament.

The lumbricals insert into the medial aspect of the extensor expansion (dorsal digital expansion) of the lateral four toes. Functionally, they flex the metatarsophalangeal joints and extend the interphalangeal joints of the toes, contributing to the fine control of toe movements during gait.The first lumbrical is usually unipennate, while the second to fourth may be bipennate, reflecting their variable origins from the FDL and FHL tendons. Innervation is by the medial plantar nerve for the first lumbrical and the lateral plantar nerve for the second to fourth lumbricals, with some anatomical variation and occasional communicating branches between these nerves

Origin: Tendons of flexor digitorum longus

Insertion: Medial aspect of extensor expansion over lateral four digits

Nerve: Medial and lateral plantar nerve

Action: Flex proximal phalanges and extend middle and distal phalanges of lateral four digits

Gray's description: The Lumbricales are four small muscles, accessory to the tendons of the Flexor digitorum longus and numbered from the medial side of the foot; they arise from these tendons, as far back as their angles of division, each springing from two tendons, except the first. The muscles end in tendons, which pass forward on the medial sides of the four lesser toes, and are inserted into the expansions of the tendons of the Extensor digitorum longus on the dorsal surfaces of the first phalanges.

Variations.—Absence of one or more; doubling of the third or fourth. Insertion partly or wholly into the first phalanges.