Flexor digitorum medialis muscle

The medial digital flexor muscle (formerly flexor digitorum longus) is one of the three (or two in carnivores) proximal head of the deep digital flexor muscle that lies on the caudal surface of tibia covered by the gastrocnemius and the superficial digital flexor. 

Origin: tibia and the fascial leaf separating it from the lateral digital flexor muscle

Insertion: to the distal phalanges via the common tendon of deep digital flexor muscle

Action: Flexion of the digits

Nerve: Tibialis