Essential Facts About Equine Blemishes

These expert insights will help you distinguish harmless blemishes from potential lameness issues.

It happens at some point to all of us. You’re grooming your horse and suddenly notice an odd lump, bump, swelling or unevenness on his leg. Your first thought might be, Was that there yesterday? But your next thought is most likely, Should I worry?

The answer, of course, is it depends. The good news is, if it’s a blemish, you can relax. To help you assess the situation and determine whether a blemish is all you’re dealing with, we gathered expert insights from Mark Holman, DVM, owner of Boston Equine Associates in Rehoboth, Massachusetts, an equine practice focused on evaluating soundness and improving sporthorse performance. Julie Winkel, a nationally renowned judge, trainer, rider and clinician, and CEO of Maplewood Stables in Pleasant Valley, Nevada, also shares her input on how blemishes could impact a horse’s competitive success and value.

Blemish Versus Unsoundness

Blemishes are visible abnormalities in your horse’s appearance—a bulge, a bump, a scar—that don’t impact movement or performance. They tend not to change dramatically over time, says Dr. Holman, and some blemishes may even improve in appearance.

“They are not associated with active inflammation, and most do not generally require active treatment,” he explains. “In general, there is no swelling around them, they do not react to being palpated, they are not reddened and no abnormal heat is felt over them.”

Unsoundness, on the other hand, often comes with inflammation and discomfort. Unlike a blemish, an unsoundness may cause your horse to react negatively to palpation of the area, show abnormal movement or exhibit outright lameness. An unsoundness typically requires some form of active treatment to resolve.

Why Blemishes Matter

If blemishes don’t cause the horse pain and don’t affect performance, why should you care about them? First, by gaining a basic knowledge of common blemishes of the equine leg, you’ll have a better idea when it’s time to worry and call the vet and when you can relax. Understanding the differences between a blemish and an unsoundness may also help you decide whether you should rest your horse or continue with your normal riding routine when you find that mysterious abnormality.

Being able to identify blemishes can also come in handy when you’re horse shopping and assessing a horse’s competitive potential.

“Often the decision to purchase a horse may rely on knowing what impact common blemishes may have on the horse’s future success in the competition arena,” says Dr. Holman. “Some judges feel that any abnormal findings on the surface of the horse should be discounted in classes that evaluate and compare conformation between horses, such as the conformation hunter classes or Quarter Horse halter classes.”

Winkel agrees, noting that “an unsightly blemish, such as a large scar in a highly visible place [like the] neck or face, would mar the picture of an otherwise beautiful horse in the conformation or breeding classes as well as hunter classes in general. Although it doesn’t affect performance, looks are part of the overall picture.”

She recalls showing a handsome horse years ago that had a large scar on the front of his hind cannon bone. “I showed in the Regular Conformation classes, and it was 50/50 whether the judge moved us down for it or not,” she says.

Similarly, she adds, splints were once routinely considered a “big no-no” in conformation and breeding classes. (More on splints and other specific blemishes below.) Today, though, judges may be more likely to overlook this blemish, “understanding that splints happen because these horses are not hothouse flowers but athletes competing at many more shows than in the old days,” says Winkel. “I applaud these judges for evaluating horses [and] looking for the positive attributes of the horse, not the negatives.”

Winkel says that a raw or partially healed sore on a horse that isn’t an unsoundness may still raise red flags in situations where officials are looking out for spur marks or tack-related injuries, such as during an FEI (International Equestrian Federation) inspection.

Certain competition rules may even specifically comment on blemishes. For instance, the U.S. Equestrian Federation rules for judging hunters state that, “Judges must penalize but not necessarily eliminate horses with structural faults, defects and blemishes … in areas which might impair their activity and durability.”

Be sure to review the rule book for your discipline or breed if you’re worried about a blemish on your horse or a horse you’re thinking of buying.

Blemishes can also come into play if you’re trying to sell a horse because some people will only accept a blemish-free animal, associating this with quality and excellent care, says Dr. Holman. You may be able to ask a higher price for these “perfect” individuals than for one with unsightly or numerous blemishes, he adds.

Six Blemishes You Should Know

While there are many blemishes out there, these six are among the most common affecting a horse’s legs, making them essential for every horse owner to understand.

Splints. Among the most common of blemishes, splints are hard, bony deposits on the splint bones, which run along each side of the cannon bone from the knee to just above the fetlock. They are more common on the front legs and can be caused by direct trauma or long-term stress—related to repeated concussion, improper hoof balance or poor conformation—that causes a tear in the outer layer of the bone. Initially, a firm swelling forms, likely presenting with heat and possibly pain or lameness. In time, most “popped” splints will cool off, develop new bone that creates a hard lump (callus) and are no longer painful.

Splints are hard, bony deposits that are typically found on the front legs and are one of the most common types of blemishes.
Paula Da Silva/

Sidebones. These occur when cartilage on the inner or outer side of the distal phalanx, or coffin bone, ossifies or turns into bone. Sidebones rarely cause pain and can be difficult to notice—you may feel or see them as a hard, inflexible bulge on the coronet band or notice that the adjacent hoof wall appears more upright than it once was, due to the bulge from the ossified cartilage. In some cases, they may not be identified until the horse is radiographed for another reason. Like splints, sidebones can develop due to repeated concussion or direct trauma. They may be more common in horses who toe in or have hoof imbalances, with horses who work on hard surfaces and with draft breeds. Sidebones may also be a byproduct of the normal aging process.

Windpuffs. Also known as road puffs, these soft, fluid-filled swellings appear toward the back of the fetlock joint and may occur on all four legs or only on the hind legs. They’re the result of inflammation of the digital flexor tendon sheaths. Older horses and those who are worked heavily, trailered extensively or have coarse, round bones with poorly defined joints and veins tend to be more susceptible to windpuffs. They may initially be painful on palpation or when the joint is flexed, but eventually will become mere blemishes with no associated lameness, unless the tendon or tendon sheath is reinjured.

Bog spavins and thoroughpins. These occur when excess fluid accumulates and forms into soft swellings around the hock joint. Bog spavins appear on the inside front of the hock, while thoroughpins appear above and on the back of the hock. They may be caused by osteochondrosis that results in chips of cartilage or bone irritating the joint, leading to an increase in fluid. Severe injury or strain may lead to bog spavins or thoroughpins, and horses with too-straight hocks may be more prone to these blemishes.

Capped elbows and capped hocks. These are a thickening of the skin, like a callus, on the point of the elbow or point of hock. They’re most commonly caused by repeated contact with a shoe when the horse lies down. Shoes with caulks may be more likely to cause trouble than a standard shoe, but either can cause this blemish. Capped hocks may also result if a horse frequently bumps his hocks inside a short trailer or one with an unpadded tail gate.

A capped hock (a thickening of the skin, like a callus) is a common blemish that can be alarming at first, but it is not usually a condition that causes the horse discomfort.
frederic chehu/

Old bowed tendons. Initially, a bowed tendon is caused by an injury to a tendon in the lower leg, creating lameness. Once the injury heals, the site may remain noticeable as a thickening on the back of the leg, above the fetlock. An old bowed tendon is often considered a blemish. However, the tendon typically is weaker and stiffer than before the bow, and the horse may be sound yet unable to perform at the same level as before the injury, says Dr. Holman.

Making the Call

If you’re still not sure whether that mysterious lump, bump or other abnormality is something to worry about, go back to basics. If it causes your horse discomfort, the safe bet is to have your vet check it out. If it doesn’t, then keep an eye out for changes—but meanwhile, take a breath, relax and enjoy your horse.

Conformation May Increase the Risk

“It is interesting to know that some conformation abnormalities may lead to the development of certain blemishes,” says Mark Holman, DVM, owner of Boston Equine Associates in Rehoboth, Massachusetts. For instance, a horse who turns out from the fetlocks may move narrowly in front with the legs swinging inward. This horse is at higher risk of hitting his own inner fetlock with the opposing hoof, which may lead to thickening of the skin and scarring on the inside surface of the fetlocks, he explains.

Certain types of conformation faults, such as a horse who toes out, can contribute to the development of certain blemishes.
Paul da Silva/

Similarly, Dr. Holman adds, a horse with offset knees—where the cannon bone is set more to the outside of the knee rather than under the center—or with legs that deviate outward below the knee may be more prone to developing splints. This is due to the asymmetrical loading forces on the cannon bone and splint bones caused by the structural deviation. Similarly, horses with extremely long cannon bones may be more prone to bowing the tendons. That’s because longer cannons are associated with longer, thinner, weaker tendons, explains Dr. Holman. 

When Blemishes Aren’t So Harmless

A hallmark of blemishes is that they don’t directly cause unsoundness. However, they may sometimes indirectly cause rideability issues. For instance, the location of a blemish could impinge on other structures, such as bones or soft tissue, and lead to performance problems related to those other structures. A splint could cause trouble if its location interferes with the movement of the carpal (knee) joint in the front legs or if it’s hit by the opposing hoof, says Julie Winkel, a nationally renowned judge, trainer, and CEO of Maplewood Stables in Pleasant Valley, Nevada.

In fact, Mark Holman, DVM, owner of Boston Equine Associates in Rehoboth, Massachusetts, recalls a case where a horse had splints that caused no trouble for years but then suddenly seemed to be causing lameness. A diagnostic ultrasound “revealed that the splint callus (or bony deposit) had enlarged to the point that it was physically displacing the suspensory ligament body and was directly placing pressure on this structure and causing bruising,” he says. “The splint callus had to be surgically removed to relieve this stress and provide more space for the ligament to move and function normally.”

In another instance, Dr. Holman says, an old splint seemed to create new pain, but it turned out the horse had hit the area with a hoof while jumping. This aggravated the splint and made the horse unsound for several weeks until the inflammation resolved and the splint became painless again, he explains.

Similarly, thick scars could potentially impact the flexibility of underlying joints or tendons, says Dr. Holman. They could even crack and, if left untreated, lead to infections. And a scar located where the girth sits may be aggravated by the girth and render the horse unusable for riding, he notes.

Close Call: Blemish or Unsoundness?

Sometimes the distinction between a blemish and an unsoundness isn’t clear cut. Here are three examples when the designation depends on details.

Scars. These are considered blemishes if they involve only the skin or subcutaneous tissue just under the skin, or if the scar moves freely, like the surrounding skin, so that it doesn’t interfere with the horse’s movement. If the scar causes sensitivity, pain or lameness, or is located in a place where it may interfere with the horse’s rideability or comfort under saddle, it would be considered an unsoundness.

Curbs. These appear as a swelling or thickening of a ligament or tendon on the top and rear of the hind cannon, almost at the back of the hock. They’re easiest to see from the side. Curbs can be caused by a number of soft-tissue injuries. They may be an unsoundness or a blemish, depending on whether or not they cause lameness. Standardbreds and horses with sickle hocks (excessive angulation of the hock joint causing the horse’s hind feet to stand too far underneath the horse) may be at higher risk of developing curbs.

Ringbone. This condition is apparent as very hard, bony-like lumps on the coronet (low ringbone, which affects the coffin joint) or just above the coronet (high ringbone, which affects the pastern joint). The lumps are caused by deposits of calcium around the edges of the joint and erosion of the cartilage surfaces of the bone, explains Dr. Holman. Instead of bone gliding on cartilage, this process can lead to bone rubbing on bone, a painful condition that typically causes lameness. Because of this, ringbone is typically considered an unsoundness. In some cases, the joints may fuse, which may eliminate pain and turn the ringbone into a mere blemish.

Ringbone is a condition in which hard, bony-like lumps appear on the coronet (low ringbone) or just above the coronet (high ringbone).
Paula Da Silva/Arnd.nL
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