The many ways conformation can affect a horse’s soundness

Whether you are shopping for a new riding prospect or already have a horse, it helps to be able to correctly evaluate conformation. Assessing limbs, feet, and body can help you and your veterinarian identify anatomical traits that could end up being performance-affecting liabilities. And, armed with that knowledge, you can take steps to help keep him sound.

Defining Imperfection

While there’s no such thing as perfect conformation, certain structural qualities and alignments are more likely to support soundness than others.

“If skeletal bones articulate (join) correctly, the line of concussion that runs up the leg when the horse hits the ground is evenly distributed all the way up the limb,” explains Kylee Jo Duberstein, PhD, associate professor of equine science at the University of Georgia, in Athens. “When a horse has a conformational defect—toed in or out, offset cannon bones, benched knees, sickle-hocked—bones don’t line up correctly at the joints. This results in uneven distribution of concussion each time the limb impacts the ground, with one area of the bone, joint, or soft tissue structures assuming excessive impact.”

She cautions against getting hung up on “absolutes” such as which conformational flaw is better or worse than another. Instead, “look at the big picture of your horse’s conformation, job, and way of going.”

Dynamic Motion vs. Static Structure

When considering conformation, Chrysann Collatos, VMD, PhD, Dipl. ACVIM, of High Desert Equine, in Reno, Nevada, says watching a horse in motion always trumps looking at him standing still. She cites an example of a horse with contracted heels or a club foot in front yet a strong, symmetrical, well-conformed pelvis and hind limbs.

“Contracted heels or a club foot may predispose a horse to concussion-related foot lameness,” she says. “However, (such) a horse may have conformational characteristics that are able to be trained for maximum locomotor efficiency, such as the ability to move with impulsion from behind, raise its withers, and engage its core. This horse can develop an overall ‘lighter’ movement that reduces concussive force on the feet and limbs to mitigate the development of forelimb lameness resulting from poor hoof ­conformation.”

The team in Duberstein’s lab is performing preliminary research on balance, weight distribution, and soundness in horses. She describes how the forelimbs and hind limbs function differently: “The hind limbs generate tremendous propulsion, but more in a horizontal manner, while the front limbs tend to generate a vertical force to push the horse upwards off the ground.”

Horses naturally carry 65-70% of their body weight on the front end. Certain conformational flaws, such as being built downhill (croup higher than the front end and/or a low-set neck), cause a horse to carry even more weight on his forehand.

“Riders often have the objective of ‘lightening’ a horse’s front end under saddle by spending time worrying about head position,” says Duberstein. Many times what riders are creating is just the appearance of suppleness, however, with energy/impulsion never really coming from behind and the horse not stepping up under himself and moving into the bridle properly.

“It is important to remember that a horse isn’t a cheetah or a greyhound, and no matter how hard horses are pushed to achieve a specific body position under saddle, their spine (in the thoracic, lumbar, and sacral area) doesn’t really bend,” she continues. “As herbivores, horses have a heavy GI tract with a very rigid spine to support that weight. Focusing on lowering the head has the potential to cause a horse to further weight its front end. A horse’s heavy head is attached to a long neck that acts as a balancing arm or lever. Wherever the head moves, body weight tends to follow.”

Riders in many disciplines desire certain neck sets and conformation that lead to musculoskeletal issues, says Collatos. “Conformation of the cervical (neck) spine is critical for creating a connection from the poll to the base of the tail,” she explains. “It is with increasing frequency that osteoarthritis is diagnosed in the mid and lower cervical vertebrae, using ultrasound and advanced imaging such as CT (computed tomography). When an owner complains about tripping, subtle or inconsistent forelimb lameness, or difficulty in transitions, cervical arthritis is on my list of potential differentials.”

Collatos says she tends to avoid a ­low-set neck conformation for upper-level dressage or show jumping prospects. “The base of the neck should be level with the point of the shoulder or higher,” she says. “The set of the neck relative to the shoulder is significantly more important than the length of the neck.”

Duberstein stresses, “Balance and structural correctness have always been two main criteria in judging a horse’s conformation, and probably for good reason. Horses that carry themselves in a way that generates less impact when they land likely do less damage to bones and joints than those individuals that come crashing down with each step.”

Sport-Specific Effects of Conformation

Some conformational traits are more likely to affect horses’ soundness and performance depending on the discipline.

“Carpal arthrosis is more common in racehorses due to hyperextension of their carpal (knee) joints when they fatigue,” says Duberstein. “So, it is sensible to avoid conformational problems like being calf-kneed (back at the knee), which potentially exacerbates hyperextension of these joints. Jumpers, reiners, and cutting horses are prone to hock arthritis, so straight hind leg or sickle-hocked (small hock angles) conformation traits are liabilities. Many sport horses are also prone to ringbone (pastern or coffin joint arthritis) and suspensory ligament injuries; therefore, alignment of the bones in the lower limb is also important.”

Suspensory ligament injuries are common and serious causes of lameness in all disciplines. For this reason both Collatos and Duberstein try to avoid limb conformation that might predispose a horse to suspensory ligament desmitis (SLD, inflammation of that structure), including straight hock conformation and long cannon bones and pasterns.

“Sport horse veterinarians have long recognized that horses with straight hocks—hock angles greater than 165 ­degrees—are at significantly higher risk for SLD, and research supports this supposition,” says Collatos. “Endurance horses experience repetitive concussion at moderate speeds for many consecutive hours. Soft tissue fatigue develops insidiously throughout a competition; therefore, long, sloping pasterns are a risk factor for development of forelimb suspensory injury in (these) distance athletes.”

Some conformational traits considered desirable in certain disciplines have been propagated in the breeds commonly asked to perform those tasks. When you choose a horse (or choose a career for a horse you have), says Collatos, consider your athletic pursuit and how the horse’s conformation will affect his ability to perform in that endeavor: 

• Quarter Horses are bred to work cattle, and a lower headset facilitates rapid turns with exceptional speed and quickness from the hindquarters. Therefore, Quarter Horse conformation tends to be downhill with tremendous power and musculature in the sacrum, hips, and thighs to enable them to dig in, turn, and go.
• Thoroughbreds are bred to run and are apt to have a croup that is slightly higher than the withers. That might or might not offer them a speed advantage but has been bred into many lines of racehorses.
• Arabians, as the ultimate long-distance athletes, are generally balanced front to back, with lean muscle mass and shoulder angles that optimize efficiency at moving across the ground with minimal effort or limb lift.
• Warmbloods are bred to have a combination of elevated movement and elongated stride. They generally appear somewhat uphill in their balance, with a neck that comes relatively high out of the withers, a moderately sloped shoulder, and a very powerful sacrum and pelvis. 
• Draft horses are bred to pull; they tend to have an uphill build with short, strong, high-set necks, powerful shoulders, and relatively weaker hindquarters than other breeds.

Overall balance and locomotor efficiency are extremely important to a horse’s athletic longevity and ability to compensate for lower-limb defects, says Collatos. However, training can help develop core strength and flexibility to markedly enhance a horse with less-than-ideal balance or limb conformation. 

Preventive and Corrective Measures

One strategy for preventing lameness, no matter the horse’s conformation, is regular and correct hoof trimming and/or shoeing. “Whether barefoot or shod, the resilience to withstand the stresses of competition and to achieve athletic longevity is enhanced by a balanced foot,” says Collatos. “It is critical that the farrier examine the entire bony column of the horse and balance the foot with respect to the weight-bearing forces that result from all aspects of a horse’s conformation. A good farrier balances the horse, not just the foot.”

“In horses with limb deviations, hoof angles tend to develop imbalances more quickly than horses with good limb conformation because the way the crooked leg moves causes uneven wear on the hoof,” adds Duberstein. “A good first step is to work with a competent farrier to maintain a regular trimming and shoeing schedule that ensures keeping a horse’s hoof angles as correct as possible for that individual.”

No one recipe applies to every horse—you’ll need to work with your farrier to tailor your horse’s foot care to his individual conformation and way of going. Collaborate with your veterinarian, as well, using radiographs (X rays) to evaluate hoof angles and foot placement and guide shoeing and trimming ­recommendations.

Attempts to correct some foot deviations, such as shoring up low heels on a long-toed horse, can lead to further problems, notes Collatos. “Raising the heel with a wedge pad actually lowers the fetlock to result in serious negative effects on soft tissue dynamics within the foot,” she says. “A wedge pad also increases ground pressure forces through the heels, which actually reduces heel growth,” when the goal should be to promote it.

Using shoe branch extensions to attempt to twist a horse’s toed-in or toed-out conformation to what is considered “normal” can also create long-term problems, pain, and lameness.

Another strategy for helping horses deal with conformational flaws is sound conditioning. “Horses are more likely to suffer a severe injury when they fatigue,” says Duberstein. “The muscles, especially in the limbs, stabilize the leg and keep joints from hyperflexing or hyperextending as each limb impacts the ground.”

Muscle fatigue diminishes this ­stabilization ability, allowing joints to move beyond their normal range of motion, she says, and potentially causing severe and acute damage to cartilage, bones, and soft tissue.

“Horses with limb deviations often don’t travel with their legs staying in one plane—they tend to wing in or wing out,” Duberstein continues. “Fatigue amplifies such busy limb motion, making the horse more likely to interfere (one foot hitting the other leg) in addition to adding impact more on one side of the hoof and limb than the other.”

Conditioning a horse properly goes a long way toward delaying the onset of fatigue, and using leg protection can help prevent interference injuries.

Repetitive motion can lead to osteoarthritis development over time. So, there’s a fine line between conditioning a horse to prevent fatigue that could cause acute injury and trying to minimize inevitable wear and tear that comes with repeated movements and impact, says Duberstein. This is particularly true for disciplines that rely on speed, distance, and/or agility.

Rather than trying to patch up already-developed lameness issues with palliative care such as joint injections, take a proactive approach by properly selecting and conditioning a horse for your desired athletic enterprise—or selecting a sport in which your horse will excel—and having him correctly shod. Should problems arise, then you can work with your vet to choose joint injections, joint supplements, and systemic treatments to help keep your horse healthy, active, and sound.

Take-Home Message

To have the best chance of a sound horse, first select one “with good all-around conformation, keep hoof angles balanced, maintain the horse at a healthy weight to avoid overtaxing the musculoskeletal system, provide plenty of turnout, and condition him properly to do the job you are going to ask him to do,” says Duberstein.

Then, “stand back and look at the whole picture—the entire horse—not just the offset knee or base-narrow stance or turned-out toes,” says Collatos. “Developing a horse’s entire body to be strong at the center and balanced from front to back helps overcome many conformational problems.”

If conformational liabilities affect a horse’s performance in a specific sport, then you might ultimately need to find a different horse for that pursuit and point him toward another sport that capitalizes on his strengths and abilities.