Conformation in Horses
Conformation...what does it mean? If you've spent any time around horses or horse people, you've heard this word or related words used again and again. "Wow, that horse has great conformation!" or "My trainer said not to buy that horse because he has such horrible conformation--he won't hold up." Conformation is discussed so frequently because it often is what makes horses better able to perform their job, or at least can help them have longevity in regard to performance. Horses with good conformation are prized and usually more valuable than a counterpart with poor conformation.
Over the years, people have created numerous terms to describe conformational faults or flaws in horses--I'm sure you've heard a few. For example, "That horse is gorgeous, but he's pigeon toed." Or how about, "I really liked that hunter, but he's got an ugly club foot." Then there's the, "So what if the horse has 'bad' conformation, he can jump the moon."
Does conformation really have anything to do with performance? Does bad conformation eventually cause lameness? What are some of the more common conformation flaws to avoid?
In this article, we will discuss the good, the bad, and the just plain ugly aspects of conformation in horses.
What Is Conformation?
Conformation, according to Ted Stashak, DVM, who wrote The Horseowner's Guide to Lameness, is the outline of a horse as dictated primarily by his bone and muscle structures. However, conformation is not just straight legs, it also is about the length of the bones, the angles of the joints, and the proportions and overall balance of the horse.
Conformation is related to the breed and use of the horse. For example, a Quarter Horse used for Western pleasure will have a different ideal conformation than an Arabian used for saddleseat, especially in regard to desired muscling, length of neck and back, straightness of the top line and croup, and way of traveling.
So, some aspects of conformation really do depend on breed and purpose. While it would be easier to fill the entire magazine with descriptions of desirable conformation for each breed or type of horse, instead we will concentrate on undesirable conformation, which practicaly is the same for all breeds.
How Do You Evaluate Conformation?
Conformation in horses should be evaluated carefully, and all good judges, veterinarians, and horse owners should have a system to prevent missing any aspect. Each person has a system which works for him, so if you are curious, ask a respected individual in your area, or attend a judging clinic.
In brief, the horse should be viewed from each side, making sure to evaluate the horse at a standstill and while in motion (walk and trot). The fore and hind legs should be evaluated for straightness, correct angles, slope, muscling, and proportion. The pelvis and croup are evaluated for symmetry, length, and straightness. The head and neck are evaluated for normal balance and appropriate length and curvature, with special attention being paid to the teeth and bite.
To help you evaluate whether the horse's legs are straight, you can imagine a plum line (a piece of string with a weight at the bottom allowed to swing freely and hang straight). If standing in front of or behind the horse, imagine the line from the point of the shoulder (front)/tuber ischium (back) straight to the ground. The line should intersect the carpus (knee)/tarsus (hock), fetlock, pastern, and hoof in the middle of each structure. However, when viewing a horse from the side (profile), a line can be drawn from the top of the scapula/tuber ischium down the leg. In the hind leg, the line should follow the back of the hock and cannon bone to the ground. In the foreleg, the line should intersect the carpus and fetlock in the middle of the joints.
This is an extremely brief description of evaluating a horse for correct conformation as the purpose of the article is to discover and evaluate conformation flaws. So, let's talk about the bad.
What Are Conformation Faults?
Faults or flaws in conformation can occur in the forelegs, hindlegs, pelvis, head, and even the neck. For this article, we will mostly concentrate on faults of the fore and hind legs. These conditions are undesirable, not just because they don't meet a breed standard, but because they cause inherent weakness in the legs and predispose the horse to lameness or injury.
Many of these problems are present at birth or soon after, and they are correctable, if they are recognized. However, many of these faults go unnoticed until the horse is one or two years of age, and then it is too late to correct the problem. At that point, they are permanent baggage for the horse and the horse owner, leading to abnormal wear of the joints, tendons, and/or ligaments.
Following are descriptions of common conformation faults (with the lay term in parentheses).
A club foot is a term that describes a hoof with a foot axis of 60 degrees or more. This condition can be acquired (developed ) or congenital (present at birth). This condition occurs almost exclusively in the forelegs. If the club foot is congenital, it results from a congenital flexural deformity "contracture" of the deep digital flexor tendon. An acquired club foot often is the result of an injury or condition that causes pain in the leg, resulting in disuse. The leg then develops a flexural deformity from the disuse, and the hoof changes shape as a result. An acquired club foot also can be the result of nutritional problems, leading to the same flexural deformity.
Treatment is aimed at eliminating the inciting cause and returning the hoof to a normal angle through corrective trimming or shoeing.
Toed-In (Pigeon Toed)
This flaw is recognized when viewing the horse from the front. One or both hooves will point inward. The deviation can begin at the shoulder or hip, or as low as the fetlock. This conformational abnormality--like many of the others--is congenital in nature, which means it is present at birth. This problem usually can be completely corrected with corrective trimming and shoeing, but the correction must start at an early age to be successful (by one to two months of age).
This problem is frequently seen with angular limb deformities, so correction of the angular limb deformity with surgery often is necessary. Toed-in conformation leads to aberrations of the leg during flight; the leg will travel in an outward arc (paddling) during movement. The toed-in conformation leads to excessive strain on the outside or lateral aspect of the hoof and fetlock, as the horse usually lands on the outside wall of the hoof.
This flaw also is recognized when standing in front of the horse. One or both hooves point outward (opposite of toed-in). Like the previous flaw, toeing-out is a congenital problem, and can originate from the shoulder/hip or lower in the leg. Unlike the forelegs, it is normal for the hooves of the hindlegs to point out slightly. This is a result of the normal position of the stifle in the horse, which is turned out slightly.
Again, like toeing-in, an angular limb deformity such as a valgus (turned outward) deformity, can exacerbate the problem. The angular deformity might require surgery; however corrective shoeing and/or trimming beginning as a young foal usually can correct the outward deviation of the hooves. In these horses, interfering of the foot and fetlock can occur, resulting in injury to the fetlock.
Carpal Valgus (Lateral Deviation Of The Carpus; Knock Knees)
Carpal valgus is one of the angular limb deformities that occurs in foals. These congenital deformities are common, but easily corrected, either with rest and trimming/shoeing or with surgery. We do not understand why they occur; theories include heredity, malposition within the uterus, and nutritional factors. Carpal valgus is when one or both carpi (knees) deviate outward when viewed from the front. If left uncorrected, this results in a great deal of stress placed on the ligaments and small bones of the carpus, especially on the medial or inner surfaces of the carpus.
Although most of these deformities will correct spontaneously if mild in nature, those that are more severe or do not correct on their own require surgery within the first two months of life. After that time, the growth of the radius has greatly slowed and there is a much less chance of a successful outcome.
Carpal Varus (Medial Deviation Of The Carpus; Bow Legs)
Carpal varus is another angular limb deformity that occurs in foals and is the opposite of carpal valgus. Carpal varus is when one or both carpi (knees) deviate inward. This results is the stresses being greatest on the lateral or outer surface of the carpus. Like carpal valgus, this deformity should be corrected early to decrease the abnormal stresses placed on the small bones of the carpus and prevent injury.
Palmar Deviation Of The Knee (Calf Knee)
This conformation flaw is best seen from the side of the horse. In an animal with this flaw, if a straight line is drawn from the scapula (shoulder blade) to the hoof, the carpus will be behind the line. This fault greatly weakens the carpus and can lead to chip fractures of the radius and/or carpal bones, especially in racehorses because of the fatigue factor at the end of a race.
Dorsal Deviation Of The Knee (Over At The Knee)
Adults and foals with this flaw are best recognized from the side. A straight line from the scapula to the hoof reveals that the knee is in front of the line. The horse might appear to be buckling forward at the knee. A congenital problem in foals, it is thought to be due to "contracture" of the tendons in the back of the knee. Treatment for these foals includes splints and air casts to help straighten the leg, accompanied by treatment with oxytetracycline (an antibiotic that is thought to work by binding calcium and relaxing the muscles in the leg to allow lengthening).
Base Narrow (Stands Close)
Another conformation fault is a horse with base narrow forelegs. This condition is recognized from the front of the horse, with the distance between the horse's forelegs being less at the hoof than at the shoulder. These horses typically have overdeveloped chests (pectoral muscles). This deformity leads to lameness problems such as ringbone (osteoarthritis of the pastern or coffin joint). The ringbone usually results because this flaw in a horse forces it to bear weight unevenly, with the horse landing on the outside of the hoof first. This uneven loading of the foot is the reason for the development of osteo-arthritis.
Base Wide (Stands Wide)
The opposite of base narrow, this flaw is recognized as the distance between the horse's forelegs being less at the shoulder than between the hooves. Breeds with less-developed pectoral muscles more commonly are found to have this condition. As in base narrow horses, base wide horses abnormally load the joints of the lower leg, with the most stress being placed medially or on the inside of the legs. Ringbone commonly results from this conformation flaw.
Offset Knees (Bench Knees)
This conformation flaw is best seen from the front of the horse. This flaw gets its name because the cannon bone is placed too far laterally or to the outside of the knee--offset. A line from the scapula down the leg would intersect the radius in the middle of the bone, but the line would be on the inside of the cannon bone. This conformation results in more stress being placed on the medial side (inside) of the cannon bone, especially on the medial splint bone. This flaw often results in horses with medial splints.
Straight Hocks (Post Legged)
This conformation flaw of the hind legs is best seen from the side of the horse. In normal horses, there is a small, gentle angle between the tibia and the cannon bone within the hock joint. In a horse with straight hocks, there is little angle between the tibia and cannon bone (hock joint) and tibia and femur (stifle joint). Therefore, the leg has the appearance of a post. This conformation predisposes to osteoarthritis of the hock and problems with the patella within the stifle joint.
Large Angulation Of The Hock (Sickle Hocks)
This conformational flaw of the hocks is best seen from the side of the horse. While in post-legged horses the hock is very straight, in sickle hocked horses the angle of the hock joint is too small and results in the cannon bone being too far underneath the horse. This conformational defect leads to stressing of the structures at the back of the hock and cannon bone, especially the plantar ligament. This ligament can be strained or injured in heavy exercise in horses with this conformation.
Unsightly, Not Unstable
And now for the ugly. These conformational defects do not necessarily hinder performance or result in lameness, but are they are definitely not attractive.
Exacerbated Lordosis (Swaybacked)
This conformational flaw is more common in older horses with long backs. It also is seen is some older broodmares. In longer backed horses such as American Saddlebreds, the ligaments that support the lumbar vertebrae begin to sag, thus allowing the back to sway. There is no treatment.
Brachygnathism (Parrot Mouth; Overbite)
This is a congenital conformation defect that is characterized by the lower jaw or mandible being shorter than the upper jaw. This is the most common oral conformation defect in the horse. Normal horses should have contact between the surfaces of the upper and lower teeth (arcades). A severe overbite results in difficulty chewing, and frequent dental work is required. Surgical treatment with wires to inhibit the growth of the upper arcade can be performed to help correct the deformity. However, because this condition is thought to be hereditary, many veterinarians will not perform the surgery unless the foal is neutered.
Prognathism (Monkey Mouth; Underbite)
This oral conformation fault is the result of the lower jaw being longer than the upper jaw. This condition is less common than the overbite, but the treatment is the same.
Horses with a ewe neck often are said to have their necks attached upside down. These horses have a concave neck with a depression just in front of the withers. A ewe neck appears to have more muscling on the underside of the neck. Horses with ewe necks also carry their heads higher than might be desired, and usually are athletically challenged.
So, what relation is conformation to lameness? It's obvious that severe conformation defects will limit if not inhibit performance. More mild defects could lead to lameness problems such as osteoarthritis or traumatic injuries, which might mean intensive medical management or a short career.
Good conformation always has been a precedent for good performance. However, there are exceptions. Horses which defy the odds and run faster, jump higher, and just plain outperform their more correct counterparts do exist. These horses have something else going for them--an indefinable nature that makes them a winner.
Adams, O.R. Adams Lameness in Horses, edited by Ted S. Stashak, DVM, MS, DACVS, Lea & Febiger, Philadelphia, 1987.
Auer, J. Equine Surgery, W. B. Saunders, 1992.
Stashak, Ted. Horseowners Guide to Lameness, Lea & Febiger, Philadelphia, 1985.
About the Author
Christina S. Cable, DVM, Dipl. ACVS, owns Early Winter Equine in Lansing, New York. The practice focuses on primary care of mares and foals and performance horse problems.
POLL: Radiographs for Hoof Care