Flexor digitorum lateralis muscle

The lateral digital flexor (formerly flexor hallucis 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: Caudal surface of the proximal three-fifths of the fibula and the proximal caudolateral border of the tibia and the interosseous membrane.

Insertion: to the distal phalanx(ges) via the common tendon of deep digital flexor muscle

Action: Flexion of the digits

Nerve: Tibial