Pain causes many changes in hind limb movement. These changes affect flexion of joints, strain on ligaments, hoof and limb flight, hoof landing/loading and muscle tension.
Veterinarians and farriers frequently try to modify shoes so that they will have an effect on breakover, limb flight and landing and ground reaction forces placed on the hoof with the thought that these modifications will relieve pain and therefore improve overall hind limb mechanics. However, it is unclear whether the modifications that are used or have been recommended have an effect on hind limb biomechanics, as there is no research or current literature to support these modifications.
It is the author’s opinion, that all farriery begins with the appropriate trim and that any modifications merely make adjustments that may help by relieving pain, preventing further injury or easing movement.
Before discussing farriery for the hind foot, a brief description of hind limb movement is essential (Figure 1 Above). Protraction, the foot lifting from the ground, begins with the flexion of the hip, stifle and hock, which overcomes the inertia of the hind limb so minimal muscular work is done. The hip joint is flexed by the iliopsoas muscle, the stifle is flexed by the biceps femoris muscle and the hock flexes as a result of the reciprocal apparatus. The fetlock also automatically flexes because of the tendinous nature of the superficial digital flexor tendon that travels from the hock to the pastern.
Retraction is accomplished by the middle gluteal muscle…