The flexor digitorum longus muscle is a muscle in the deep layer of the posterior compartment of the leg on the medial side. It's tendon passes through the tarsal tunnel and it is the "D" in the Tom, Dick, and very nervous Harry acronym.
Action: Flexes digits 2-5, plantar flexes ankle
Innervation: Tibial nerve
Origin: Tibia
Insertion: Distal phalanx digits 2-5