Foot Problems Lead to Leg Problems
By William E. Jones, DVM
The world's best known expert on clinical problems of the horse's foot is Dr. William Moyer, head of large animal medicine and surgery at the Texas A&M College of Veterinary Medicine. In addition to years of practical experience treating foot problems on and off the racetrack, he is an entertaining speaker, and he is frequently asked to speak on foot problems at veterinary meetings around the world.
Dr. Moyer calls it as he sees it, often giving advice and opinions which run counter to common ideas on causes and treatments of foot problems. He takes great delight in interjecting common sense into a discussion of hoof balance, pointing out that many horses with so-called "unbalanced and asymmetrical" feet continue to have successful racing careers.
Speaking at the Dubai International Equine Symposium last March, Dr. Moyer said that the weakest link in the chain of factors which bring success to the racehorse is probably the feet. "There is simply little natural protection between the skeleton of the horse and the training and racing surfaces," he said, "Many of the factors affecting the feet are in combination with one another and are often difficult to correct." He talked about several of these factors.
He said that a common foot problem in Quarter Horses and Thoroughbreds used for racing is a "low heel- long toe." The very low heel is one with the coronet close to the ground with the slope of the heel almost parallel to the ground. This low heel is in conjunction with a long toe which also demonstrates a similarly low angle. This abnormality results in poor shock absorbing capability, especially in the back half of the foot.
Dr. Moyer said, "Many horses are simply born with a relatively low heel, and the incidence is sufficiently high that less severe variations of this configuration are considered by some as being normal. Toe length determines the length of the lever arm over which the limb rotates. The greater the toe length the greater the lever arm affect, and the more prolonged is foot breakover."
The point he made was that this results in greater tension on the support system of the limb- the flexor tendons, suspensory and other ligaments. This can lead to bowed tendons and other problems. This increased toe length can also be detrimental to the joints: knee, fetlock, pastern, and coffin. Improper foot trimming and shoeing often exaggerates this problem. For example it is common to raise the toe with a toe grab on the shoe.
Another factor in racehorses which leads to foot problems is flat feet. Dr. Moyer said, "The sole of the foot is the thin horny tissue inside the hoof wall on the ground surface. Normally, and ideally, the sole is concave. Immediately above the sole and interposed between it and the coffin bone is a highly vascularized sensitive sole. Ideally the majority of the sole is not intended to accept the energy of impact. The flat footed horse experiences continual and abnormal impact on the sole and the sensitive sole is easily bruised. In severe cases, the coffin bone may ultimately be involved and manifested as pedal osteitis or solar margin fractures. This problem is enhanced by training or racing on hard surfaces. A painful foot or feet can lead to damage elsewhere on the limb or limbs as a result of attempting to avoid pain and altering the gait."
Why do some horses have flat soles? This detrimental foot conformation may have been genetically acquired. According to Dr. Moyer, "It is often seen in combination with the low heel- long toe shape." Excessive trimming of the hoof, and shoeings with hoof pads can cause flat soles to develop. Actually, it is long-term excessive moisture on the sole which leads to a weakening of the protein matrix in the sole, allowing it to lose its proper concave shape. This can come from continual wet ground, or bedding; from continual washing, especially with detergents. Full pads on the sole may get wet and keep moisture against the sole.
Traction devices on shoes can cause foot problems. These include toe grabs, block heels, and heel calks. Dr. Moyer points out that gaining traction may give the horse an edge in a race, but "excessive traction can alter motion or create focal impact which can injure the foot." The most dangerous addition to a shoe is the outside "sticker," on a hind shoe. This provides the potential for abnormal torque, or spin, to the leg which can lead to injury. One additional problem with toe grabs on the hind feet is that when over-reaching occurs, they can act in a knife-like manner on the front foot or leg.
Traction devices on racing plates is not permitted in some countries, according to Dr. Moyer. Certainly there is less chance for injury without them. The trainer and farrier should be asking themselves, "when is traction excessive, and when is it necessary to prevent slipping?" Less severe shoe implants should always be considered.
Improper shoeing is common at the track, even by the most popular farriers, because of common misbeliefs. Dr. Moyer said, "It is not at all unusual for racehorses to be under shod; that is, shod with shoes that are decidedly shorter than the bearing surface of the properly trimmed foot." Whether this is done in an attempt to prevent shoe pulling, or because of tradition, the ultimate effect is that of reducing the bearing surface of the foot and creating the same effect of the low heel- long toe configuration. Some farriers will bend the inside branch of the shoe so that it is hidden under the sole and cannot be stepped by the rear foot. This can put pressure on the sole, where it should not be, causing bruising and lameness.
Improper hoof trimming is often a factor leading to foot problems and even leg injuries. Hoof trimming influences the manner in which the foot makes initial contact with the ground. Over trimming one side of the hoof wall will concentrate initial impact to the long side and apply unnatural forces through the foot and associated joints. "Because of the elastic nature of the hoof this can lead to abnormal hoof shape and chronically effect the foot or limb in the form of sheared or crushed heels," Dr. Moyer said.
"Perhaps one of the most difficult problems facing the Quarter Horse and Thoroughbred racehorse farrier is that of relatively thin hoof wall material into which nails are driven. This is particularly true of the inside quarter wall," Dr. Moyer said. "It is not unusual fort he wall to be a quarter of an inch or less thick. This means that a horseshoe nail can only be placed with little or no margin of error. If it is placed too close to the external surface, it has very little anchoring mass; and conversely if it is placed deeper it is likely to be into or next to sensitive tissue." He pointed out that the likelihood of poorly placed nails is increased because most racing plates have machine punched nail holes, predetermined to fit a symmetrical foot- which does not occur in nature with any regularity.
The term "No foot, no horse" is much over used, but it is a very profound reality in Quarter Horses that race. When confronted with a lameness which is difficult to determine the origin, the wise trainer will take heed of Dr. Moyer's advice and look first at the foot as a cause.