A Chip Off the Ol' Joint

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A broken bone is never good news. But when the break is really a bone chip, the situation may be far from dire. In some cases, bone chips don’t even need treatment and won’t affect your horse’s soundness or performance. That’s particularly good news since some experts believe as many as 15 percent of horses acquire bone chips before they’re even old enough to start training. Others estimate that anywhere from 20 to 50 percent of horses will incur a bone chip at some point in their lives. With such a high rate of prevalence, it makes sense to arm yourself with knowledge about this potential problem.

Sand and Pearls

Also known as chip fractures or osteochondral fragments, bone chips can occur on any joint in the horse’s body, but are most commonly seen in the front fetlocks and knees. They are literally pieces of bone that chip off the joint surface. Sometimes the fragments break completely off and float freely within the joint. More commonly, they detach only partway and remain partially attached to the joint.

“...20 to 50 percent of horses will incur a bone chip...”

Bone chip fragments can range from the size of a grain of sand to the size of a toenail. However, it’s not the dimensions that matter, according to Larry Bramlage, DVM, MS, DipACVS, a veterinarian for Rood & Riddle in Lexington, Ky. What matters, he says, is the amount of sand-like debris shed when the pieces of damaged bone rub against each other. More debris is likely to be shed when the chip remains partially attached to the joint and when the chip is located in a high-motion area.

The debris acts somewhat like a small stone in your shoe, causing discomfort and reducing performance ability. It may lead to inflammation and lameness and it can cause soft-tissue injuries if the horse places more weight (stress) on his “good” legs.

The good news is that not every chip leads to debris in the joint, nor does every chip result in pain and lameness for your horse. Bramlage explains that chips that completely break off often lodge in what he calls “cul de sacs” of the joint. There, the horse’s body will usually isolate the fragment and surround it with scar tissue. This leaves a smooth covering that won’t cause the rubbing that leads to debris shedding, pain and lameness. Bramlage compares it to the process of an oyster turning a grain of sand into a pearl. (He also notes, however, that if the scar tissue wears away over time, even formerly harmless chips can lead to trouble as the bone begins rubbing against the joint.)

No One Is Immune

We tend to hear about bone chips most often in relation to racehorses. Recently, trainer Bob Baffert has brought the condition to public attention by winning the Kentucky Derby and Preakness Stakes with Silver Charm, Real Quiet, and War Emblem—all of whom had at least one bone chip at the time of their victories. However, the problem can occur in horses of any breed, competing in any discipline.

More than breed, discipline or even age, five other factors appear to be linked to bone chips:

Defective bone. Developmental bone disorders, such as osteochondrosis dessecans (OCD) can predispose a horse to bone chips, leading to fractures even under normal work loads.

Conformation. Similarly, poor leg conformation, particularly joint-related flaws such as calf knees, bench knees or “back at the knees,” can make a horse more prone to incurring bone chips, because of uneven or extraneous stresses placed on the joints.

Condition/use. The better shape your horse is in for the work he’s doing, the less susceptible he probably is to bone chips. Horses in poor condition—or competing “over their head”—are more likely to face problems due to fatigue and stress on the musculoskeletal system.

Trauma. Concussion, direct hits and other forms of trauma can also cause bone chips.

Genetics. Certain bloodlines seem more prone to bone chips, although this has not been proven and may be more directly related to the inheritance of poor conformation and developmental bone disorders.

Three Choices

Heat, swelling, lameness and reduced performance all indicate that a bone chip may be present. But the only way to know for sure is to have radiographs (X-rays) taken. If a bone chip is identified, you have three treatment options to choose from.

Surgery. Bone chips causing lameness are usually surgically removed. These days, the surgery is typically done using arthroscopy, which requires only two small incisions made over the joint. Cost varies depending on geographic location and the vet in question, but can range from around $1,500 to about $4,000. Recovery time takes anywhere from six weeks to six months, with two to four months the average; prognosis for a return to former ability is generally quite good.

Injections. According to Bramlage, if a bone chip isn’t causing outright lameness, but is still causing irritation within the joint, the problem can often be controlled non-surgically with injections of joint fluid supplements, such as hyaluronic acid. Often, this is done in combination with an anti-inflammatory agent, such as phenylbutazone or corticosteroids. Some vets like to use a corticosteroid because it’s highly effective in reducing inflammation. However, there is controversy over this practice, since some research has shown that steroids can actually lead to joint degeneration. There is also some evidence that injections, in general, may contribute to the occurrence of osteoarthritis.

Do nothing. When a bone chip is not adversely affecting your horse’s soundness or performance, you may choose to simply leave it alone. As noted earlier, scar tissue may develop around the chip, preventing it from causing damage and pain. However, if the chip is in an area where it is likely to cause problems in the future, you may be better off removing the fragment before it has a chance to do any damage.

The treatment path you choose may depend not only on the chip’s location and its impact on the horse, but on other variables as well. These might include your budget, what you use the horse for, and the horse’s worth. Your best bet is to thoroughly discuss the problem and the possibilities with your vet. Then you’ll be able to make the best decision for the horses in your care. [sm]

Sources:

1) “Bone Chips Fall Into Different Categories,” by Larry Bramlage, DVM, for AAEP, posted on myhorsematters.com.

2) “Equine Carpal Chip Fractures,”Oklahoma State University Extension Fact sheet F-9112, by Michael A. Collier, professor of veterinary medicine, and Carolynn MacAllister, equine extension veterinarian.

3) “Bone Chips Haven’t Hurt War Emblem,” by Maryjean Wall, Herald-Leader Racing writer, posted on kentucky.com.

4) “Is Your Horse’s Soundness Chipping Away?” by Stephanie Stephens, The Horse, 7/02 issue.