This muscle is situated on the outer and front aspects of the limb between the stifle and the hock-joint. It is thick in the middle and tapering towards the extremities.

Origin. - By a short strong tendon (together with a branch from the flexor metatarsi) from a depression on the inferior extremity of the femur between the trochlea and the external condyle.

Insertion. - The tendon, which commences above the hock, is tied down by three transverse bands, one above the hock, another below it, and a third in front of it. It then passes in front of the canon, where it is joined by the tendons of two muscles, viz. the peroneus and the flexor metatarsi parvus. In passing over the fetlock-joint a synovial bursa intervenes between it and the capsular ligament. About the middle of the first phalanx (suffraginis) it is joined on either side by a strip from the suspensory ligament, and ultimately becomes attached to the coronal process of the os pedis, or foot-bone.

Action. - To extend the foot and pastern and flex the hock.