Conformation refers to how a horse is built and how his parts fit together. It affects balance, movement, athletic ability and soundness, so it is an important consideration when buying a horse. You are much more likely to have a mount who takes to its job easily and remains sound if it has good conformation for the type of work it will be doing. Though there is some variation in what is considered desirable in different breeds, it is a simple fact that form follows function, and function follows form. This means that well-functioning bodies will necessarily have a certain form, and the form they actually have will determine how well they function. Please be aware that conformation is a huge topic which can only be touched upon in a class like this. It takes years of study to become a truly good judge of conformation, but you can learn to look for certain good points and weak points. However, it is important to realize that there is no such thing as a “perfect” horse, and some horses with considerable flaws may be perfectly well suited to you and your needs.
Faults of the Axial Body (parts that are not the legs)
While some conformational faults, such as overly large ears, have more to do with aesthetics than biomechanics, others are well known to predispose a horse to lameness. Conformational faults of the axial body that can lead to lameness include:
- Coarse or thick throatlatch: Though most people think of a thick throatlatch as a problem that may interfere with a horse’s breathing, it can also lead to lameness by causing a horse to travel with its nose poking out and its head up. This, in turn, leads the neck to drop, the spine to “invert” or hollow, and the hind legs to “trail” rather than move up and under the belly to help carry the weight of the horse and rider. In this position, the back of the horse is more vulnerable to injury.
- Ewe neck: A ewe or “upside down” neck is one that attaches low to the chest, creating a undesirable curve or bulge downwards along the underside of the neck, a concave profile along the crest, and an abnormal dip in front of the shoulder blade. A horse with this conformation will have a difficult time shifting weight from the forehand to the rear legs, resulting in increased stress on the front limbs and feet. Ewe-necked horses are typically limited athletically.
- Steep/short shoulder: The degree of angle in the shoulder determines the forward reach of the horse’s front legs. The shorter and straighter the shoulder, the shorter and quicker the stride will be. This is not only uncomfortable for the rider, but has the more serious consequence of transmitting more stress and concussion to the forelimbs.
- Long back/Weak loin: A long back is a weak back. However, many horses referred to as "long-backed" actually have a reasonable back length, but are long and weak in the loin area. Such horses tend to hollow their backs and have more trouble supporting the weight of a rider, predisposing them to back-related lameness.
- Steep croup (“goose rump”): A horse with a “goose rump” has a very steep croup that places the hind limbs in an unnaturally forward position, resulting in greater strain on the lumbar spine, pelvis and hocks. While this can allow the horse to come under from behind, creating what appears to be good, “reachy” movement, the additional strain can make a horse sore up more easily.
- High croup (“downhill”) : While many young horses go through periods where they are “croup high” or “downhill”, a highest part of the croup of a mature horse should be level with or even slightly below the highest point of its withers. A downhill topline places the horse's center of gravity forward, causing the horse to travel more heavily on the forehand with consequently increased concussion and stress. A downhill build also makes saddle fit more difficult and more critical, as the saddle will have a tendency to ride forward on the horse, potentially pinching the withers and shoulders.
Faults of the Limbs (Appendicular Faults)
Front Limb Problems:
Carpus Valgus (Knock Knees): The knee of the horse is a complex structure consisting of eight carpal bones that connect to various other bones, as well as muscles, ligaments and tendons. With so many parts needing to fit and function as one, its not surprising that the knee has a whole host of possible conformation faults associated with it. One of the most common is carpus valgus, also known as “knock-knees” or being “in-at-the-knee”. In a horse with this conformation, the horse’s knee (carpus) falls to the inside of the plumb line, creating what is called an “angular deformity”, because there will be an unnatural angle where the knee connects to the forearm (radius) and/or the third metatarsal (cannon) bone. It is common to see some degree of outward rotation of the cannon, fetlock and foot associated with this deviation. Horses can have carpus valgus in one or both front legs.
Carpus valgus can result from a number of different types of abnormalities, including:
a) problems with the growth plates or other parts of the distal (lower) end of the radius, particularly one side of the growth plate producing faster bone growth than the other.
b) abnormal development and alignment of the carpal and metacarpal (splint) bones
c) incomplete ossification of the carpal bones
d) excessive laxity of the carpal joint
It is quite normal for a foal to be born with a mild carpal valgus and toed out appearance. As the foal grows and the chest widens, the limbs typically straighten out with no intervention. However, if significant carpus valgus is allowed to go uncorrected and lasts into maturity, it can predispose the horse to soundness issues. The deviation puts strain on the inside aspect of the knee, as well as the structures connected to it. This continual strain can result in tendon and ligament injuries, as well as osteoarthritis. Carpus valgus horses may also wear down the inside part of their hoof or shoe more than the outside. Please note that this condition cannot be corrected at all in a horse over 2 yrs. old, and attempts to do so through trimming or shoeing are likely to cause lameness.
Is it a deal breaker? It depends on the degree and your intended use. If you plan to ride and train hard, jump, or compete at all seriously, avoid horses with this fault. If your use will be less demanding, a mild to moderate degree of carpus valgus might be okay, but you should have a vet examine the horse carefully.
Three knee faults best viewed from the side:
Back at the Knee (aka calf or sheep knee): This is a serious fault in which there is a slight to marked ‘bowing’ backwards of the leg from a lateral view. A plumb line would fall closer to the front of the knee and further behind the heel bulb. This puts similar strain on the limb as if the horse were continually traveling downhill. Such conformation can put excess strain on various parts of the limb, including the flexor tendons, inferior check ligament, and suspensory ligament. Horses with this fault may not move well and may be prone to stumbling, as well as bone chips in the knees and soft-tissue injuries such as bowed tendons. Working these horses in deep footing should be avoided, and it is worthwhile to x-ray the knees of any horse that is back at the knee before purchasing it. Unfortunately, many horses with this structural fault do not remain sound.
Over at the Knee (aka buck or goat knee, knee-sprung, forward at the knee): Over at the knee is the most common of the “lateral view” structural deviations. Horses over at the knee will demonstrate a slight to marked ‘bowing’ forward of the leg, when viewed from the side. A plumb line falls closer to the back of the knee and slightly forward of the heel bulb. In some cases, the limb may vibrate or shake, and it may buckle easily if you push it from behind. The strain placed on the limb is similar to what the horse would experience if constantly traveling uphill. You may see a shortened stride, and the horse may place excessive strain on the superficial flexor tendon, suspensory ligament, and sesamoid bones. Riders often report feeling that they are “lurching” forward and backwards when mounted on these horses. In severe cases, horses may actually buckle at the knee and go down, putting both themselves and their riders at risk. However, many horses with this condition have long, productive performance careers.
Tied in Knee (aka tied in behind or below the knee): From the side, this conformation fault will appear as an indentation under the back of the knee at the top of the cannon bone. It is actually caused by an abnormally small carpal canal, a structure through which several tendons and ligaments must move. The result is inhibited forward movement, as the soft tissue structures behind the cannon bone – the superficial and deep digital flexor tendons and the suspensory ligament – are prevented from moving freely. Be aware that some horses may have a thick or heavy fetlock that can give the appearance of the knee being tied in, when it really isn’t. Tied in knees typically do not present the same sort of lameness risks as the previous two.
If your adult horse has any type of knee deviation, it is important to realize that you cannot change it, and efforts to alter or improve his balance through corrective shoeing are more likely to cause harm than good. The best strategy is to go cautiously with any activity, and back off if your horse starts to show any signs of soreness. Stay out of deep footing that can cause extra strain, and be avoid steep hills if you have a horse that tends to trip or buckle. If your horse is getting sore and backing off on work isn’t providing relief, talk to your veterinarian about pain medication or joint injections, both of which can be helpful in some cases. Remember that faulty conformation does not automatically mean a horse will go lame – it only shows us potential areas of weakness. It is probably best to avoid young prospects with moderate to severe knee deviations, but if you are looking at a proven campaigner with a slight fault, and the horse has not shown signs of lameness, the horse will likely continue to do just fine.
Toed in: Horses that are toed in have a rotation in the pastern area that turns their toes toward each other. This condition often occurs in conjunction with other abnormalities, such as being base wide or base narrow. Horses that toe in are predisposed to splints, fetlock and suspensory ligament problems.
Toed out: In toed out horses, the pastern area is rotated outwards, so the toes turn away from each other. Mild toed-out conformation is not considered a serious problem and can often be corrected in foals. In more extreme cases, horses may injure themselves due to the “winging in” that this problem can cause, which can make them strike the opposite forelimb when moving. Winging in is when a horse’s feet do not travel in a straight line during the forward movement of the limbs, but instead swing in an inward arc.
Rear Limb Problems:
Sickle Hocks: Small hock angles, also known as sickle hocks, is a conformation fault in which the point of the hock lines up under the buttock correctly, but the canon bone angles forward so that the horse is standing under from the hock down. In profile, the leg appears to curve forward, giving it some resemblance to a sickle. This conformation places the plantar (rear) aspect of the hock under great stress, predisposing the horse to sprain and strain of the soft tissue structures that support the back part of the hock. Most experts agree that any horse with hock angles of less than 53 degrees is sickle-hocked.
At one time, it was thought that sickle-hocked horses had some advantages in Western performance sports. As conformation expert Dr. Charles Hutton of Murray State University states, “There was a time when people, including some judges, would say that they wanted a horse whose hocks ‘set up under him’ because it made it easier for him to stop. To a limited degree, that’s true, because when you’re starting a sickle-hocked horse in training, they often do seem to have an advantage stopping. But the problem is that they get sore, and once they get sore, they quit.
“Horses with this problem are often not clinically lame – they just can’t perform all that well because it’s uncomfortable for them. Some of them do become clinically lame with what’s called a curb, which is an inflammation in the ligament of the accessory metatarsal bone on the rear of the hock. But typically, unless they’re worked real hard, they just have performance weaknesses because of soreness.”
Is it a deal breaker: Again, it depends on the degree and your use. In general, horses with severe sickle hocks should not be subjected to intensive training and competition, but if the problem is mild, you may still be able to aim high if you are careful. Explains Dr. Hutton, “If a horse is only a little bit sickle-hocked but I felt that it was a horse that was otherwise going to make it, I would ride that horse a bit differently. By that I mean that I would put less pressure on its hocks in training and slow down my progression of exercises.
“It is also very important to work with a farrier who understands that your horse has this weakness, and who would be particularly careful to keep the hoof angle in agreement with the pastern angle. I wouldn’t exaggerate it by standing the horse up, but the toes must not be allowed to become long. If you let a sickle-hocked horse get long toed in the back, you’re going to exaggerate the stresses that the sickle hock already creates.”
So, a potentially manageable problem, especially if your use is not so intense, but best avoided if you are serious about any work that involves really working the hocks – which is just about everything, from dressage to jumping to reining to barrel racing.
Straight Hocks: Straight hocks, also known as “post legs” or being “straight behind”, is a conformation fault in which the angles of the stifles and hocks are larger than normal, while the fetlock angles are smaller than normal. The result is hind legs that look straighter than normal from a lateral (side) perspective. This a particularly serious conformation fault that predisposes the horse to a variety of problems including:
· Distal tarsal osteoarthritis (bone spavin): Non-inflammatory degeneration of the lower, narrower part of the hock joint. Usually shows up as chronic, intermittent lameness that worsens with increasing athletic demands. Other signs may include reduced performance, reluctance to work off the hind end, and back pain.
· Tarsocrural effusion (bog spavin): Inflammation and presence of excessive and/or abnormal fluid in the large upper part of the hock. .Most often appears as sudden swelling of the joint, but the swelling may become chronic if the problem is not treated appropriately. Signs include variable amounts of swelling in the hock accompanied by varying degrees of lameness, though some horses will not be noticeably lame.
· Proximal suspensory desmitis: Inflammation of the upper part of the suspensory ligament. Symptoms tend to be subtle, with little or no heat or swelling, and often no obvious lameness. The horse may exhibit poor performance, changes in gait, or other signs often mistakenly attributed to other ailments. The condition is frequently bilateral and will worsen with work, when circling or in deep footing.
· Upward fixation of the patella (locking stifle): Partial or complete inability to unlock the stifle (knee) joint. Most often affects one hind leg at a time. Affected horses will have varying symptoms depending on the severity of the condition, ranging from a slight clicking, hop or hitch in the affected limb to a total inability to bring the leg forward.
· Thoroughpin: Enlargement of the tendon sheath of the deep digital flexor tendon in the hollow space between the point of hock and the back of the joint. A sign of strain, but considered a “blemish” that does not affect performance or require treatment. Takes the form of a spongy bump that may go down over time.
Horses with straight hocks are at greater risk for these problems because the straighter angles of the hock and stifle make those joints less able to dissipate concussive force as it travels up the hind limb. As Dr. Hilary Clayton of the Department of Large Animal Clinical Sciences at Michigan State University explains, “The initial 20% of stance [the period in which the foot is in contact with the ground during movement] is known as the impact phase. During impact, the hoof is decelerated and the limb is loaded passively. The joints assist in shock absorption through compression of the joint angles, and the amount of tarsal (hock) flexion affects the amount of energy absorbed. Our studies have shown that there is less flexion and, consequently, less energy absorption, in straight tarsal joints.”
Is it a deal breaker? Some horses with straight hocks will start showing problems very early in training, yet others perform quite well and are never seriously affected by the problem. Nonetheless, all horses with straight hocks should be monitored closely for developing problems. Keeping them in a consistent, moderate exercise program can help them stay sound, but activities that put excessive concussion or strain on the joints put them at a higher risk than average for injury.
Camped out: Horses that are camped out have hind legs that are well behind the point of buttock when the cannon is perpendicular to the ground. This condition is rare, but results in short stridedness and poor athletic ability. It may predispose the horse to a variety of lameness issues involving the hind limbs and lower back. Some horses may appear to be camped out if not positioned properly for examination.
Pastern Angles: Ideally, the pastern should be moderate in length and angle. The front pasterns should range in angle from 45 – 50 degrees, while the hind pasterns will appear slightly straighter with an angle range from 50 – 55 degrees. The angle of the pastern plays a significant role in determining the amount of load placed on the lower limbs.
Short, steep pasterns are undesirable and are associated with a short, choppy stride. In addition, this may predispose a horse to navicular disease by increasing the concussion on the navicular bone. Horses with this conformation may also be more prone to superficial digital flexor tendonitis.
Long pasterns are often accompanied by excessive sloping pastern angles. This places excessive strain on the tendons and ligaments of the lower limbs, as well as on the fetlock joints. Such pasterns are weak and more prone to breakdown.
Hoof Angles: While bone structure dictates pastern conformation, the hoof angle can be changed to a great degree – for better or for worse – through trimming and shoeing. In general, the angle of the hoof follows the angle of the coffin bone and should follow the angle of the pastern, creating a straight pastern-foot axis.
In horses that have rotation of the coffin bone due to founder, the angle of the coffin bone may deviate significantly from the outside angle of the hoof, thus creating a broken pastern-hoof axis that can only be observed with radiographs.
Another problem is when a horse has low heels accompanied by long toes, which breaks the foot axis forward. This hoof shape also delays the breakover of the foot, changing the way the horse moves and putting strain on the suspensory system. Breakover refers to the motion of the horse's foot as the toe leaves the ground. Breakover also refers to the point at which this motion occurs. Once thought to occur at the front of the toe, the work of Dr. Robert Bowker (MSU) has shown it actually occurs just in front of the coffin bone.
Hoof Size: For a long time, there was a trend in the stock horse world (Quarter Horses, Appaloosas and Paints) to breed big, muscular horses with tiny feet. THIS IS BAD, and most people now realize it. You want to see a nice, big, strong foot under the horse, as it needs to support a whole lot of weight! Many other aspects of the hoof can be improved with good trimming practices, and appropriate nutrition, and even the size can increase in some cases. However, genetics will determine the size of the foot to a large extent.
As for other aspects of the hoof, as long as there is no underlying issue such as chronic laminitis (see below), a “bad” foot – one with thin, shelly walls, long toes, contracted heels, underrun heels, etc. – can often be transformed into a “good” one with proper trimming and nutrition. Still, it is nice to start with great feet. A healthy foot will be quite round in shape, especially the fronts. The heel will be wide, and the frog will contact the ground and be of a healthy, rubbery consistency. The toes will be short – not “dubbed” by a farrier, but actually short. The wall and heel height will be determined by the live sole plane of the bottom of the foot, but typically, a truly healthy foot will have a front wall no longer than 3” from coronet band to the ground. We typically see hooves much longer than that, especially in shod horses. Leading hoof researchers now believe that what we are used to seeing as “normal” in the hoof is in many, many cases actually hooves with pathologically long toes, high heels, contracted heels and contracted frogs.
The foot on the left is healthy. Notice the round shape, the wide heels, and the thick, wide robust frog that makes contact with the ground. Notice also that most of the foot is behind the white dot marking the true apex of the frog. Ideally there should be 2/3 behind that dot, and only 1/3 in front. The foot on the right has contracted heels, an atrophied frog that does not touch the ground (and therefore cannot absorb shock, which is its natural purpose), and at least half the foot is in front of the white dot.