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Related to lumbricals: Flexor digitorum profundus
lumbricalssmall intrinsic plantar muscles of the foot
origin from adjacent slips of flexor digitorum longus (FDL) tendon (three bipennate muscles), and from medial aspect of FDL tendon leading to second toe (one unipennate muscle)
insertion lumbrical tendon enters each lesser toe to medial aspect, to insert into base of proximal phalanx and extensor expansion
nerve supply first lumbrical: medial plantar nerve; second, third and fourth lumbricals: lateral plantar nerve
action weak flexion of lesser metatarsophalangeal joints; extension of lesser toe interphalangeal joints, i.e. balancing tension within extensor digitorum longus and flexor digitorum longus tendons; lumbrical dysfunction is associated with lesser-toe sagittal-plane deformities