A long muscle situated behind the tibia or leg-bone, with which it is in contact.

Origin. - From the posterior surface of the tibia and the fibula.

Insertion. - After passing over the back of the hock, where it moves through a synovial membrane and is bound down by the tarsal sheath, the tendon of this muscle continues its course downward, and becomes inserted into the under surface of the pedal or foot-bone.

About the upper third of the metatarsus or canon it is joined by the check ligament, as in the fore-limb.

Action. - It flexes the foot and fetlock, and assists in extending the hock.