Common mistakes well-intentioned owners make when handling these injuries, and steps for on-farm and in-clinic care

Black Beauty was worried about his knees, and rightfully so. The beloved equine protagonist from Anna Sewell’s 1877 novel had fallen on them “violently.” And because horses have few protective soft tissue structures in their limbs, the steed was at risk of serious—even ­deadly—infection if the injuries compromised the carpal joint capsules.

Beauty got lucky: He survived. Many horses with joint wounds, however, aren’t so fortunate. Death rates in horses with joint capsule damage are high, and permanent poor performance rates are even higher. That’s why we’ve asked the experts what to do when your horse turns up with knee, hock, fetlock, or other leg joint wounds, and why.

Horses Leg Wounds Are Special

Evolutionarily speaking, horses’ legs are like our fingers and toes. Long and bony, with no muscle in the lower limb, their joints are at particular risk of complex injuries, says Philip D. van Harreveld, DVM, MS, Dipl. ACVS, with Merck Animal Health. “Below the knees and hocks, you basically have skin covering bone, tendons, joints, and tendon sheaths,” he says.

For escaping predators and winning speed classes, it’s a great design. But not when it comes to damage. “I compare horses to race cars,” van Harreveld says. “They have amazing performance, but they break down all the time.”

Poorly protected, with critical structures literally millimeters below the surface, horses’ limbs require regular attention—and quick action when problems occur, says Rolf Becker Modesto, VMD, Dipl. ACVS-LA, owner of Becker Equine, in College Station, Texas.

That’s particularly true for lower limb joints: knees, hocks, fetlocks, and joints within the hoof, as well as tendon sheaths and bursas.

The Sins (and Virtues!) of Synovial Spaces

The beauty—and weakness—of joints is their surrounding capsules. Lubricating and nourishing, synovial fluid covers the cartilage-tipped ends of connecting bones, allowing smooth joint movement as though your horse has ball bearings. The fluid is maintained in a synovial capsule, a pocket that envelops the joints, which is sealed by a synovial membrane. When it’s all closed up, it’s a perfect joint world. But if the membrane breaks—­usually due to injury—incoming pathogens (disease-causing organisms) can wreak havoc.

It’s not that the membranes are difficult to close; on the contrary, they close easily, says van Harreveld. The problem is how susceptible synovial fluid is to infection. “It’s an absolute petri dish,” he says.

Recognizable as a viscous, straw-colored fluid that might ooze out of an injured joint (not to be confused with cloudy pus), synovial fluid and the joint capsule environment itself can help bacteria flourish (low fluid shear conditions enable bacteria to colonize), rendering a sound horse lame within hours of ­infection.

Because synovial structures have such poor blood supply, it’s difficult to get antibiotics into the joint, whether given orally or intravenously, he adds. So the trick with joints is keeping pathogens out while finding a way to get antibiotics in if infections do occur.

Fortunately, most wounds don’t penetrate the synovial membrane, says Modesto; they sort of slip to the side.

When they do break, though, it’s a recipe for disaster. “An open joint is an infected joint,” Modesto says. “That is their ­weakness.”

To help avoid the veterinary and financial disasters of a full-fledged joint infection, we’ve developed a list of “synovial sins.” When owners act quickly and appropriately, says van Harreveld, their horses have a vastly improved chance of survival.

1. Let’s Wait and See

Our sources agree that wounds in the joints merit immediate veterinary assessment. Yet, many people prefer the wait-and-see approach—and that can be a deadly decision. “I wouldn’t panic,” says van Harreveld. “But I do think the biggest mistake people make is waiting too long to report it.”

Wounds near joints are considered emergencies, just like colic, he says. Veterinarians can quickly determine whether the synovial membrane was damaged (more on this later) and start treatment right away, when it’s most effective and before the cartilage is ­damaged.

“If you wait and see that the wound is going south, you’re really going to get in trouble,” says Modesto.

Smartphones can be particularly helpful, adds van Harreveld. The rise of telemedicine has enabled veterinarians to have a formal conduit for transmitting case photos and information and to generally assess wound severity before making a farm call.

“These can be lethal infections,” he says. “They can cost the horse’s life or at least his performance. But the flip side of that is if they’re detected and addressed early, the prognosis can be really good.” 

2. It’s Not That Close To a Joint

Joints and synovial capsules are complex structures that aren’t necessarily easy to map out on the surface. The hock, for instance, is actually four joints, and the knee is three. In addition, tendon sheaths enclosed in synovial capsules branch out from those joints—most problematically, as far as wounds go, in the back of the fetlock or pastern, where a horse owner might not expect it. So, knowing how close a wound is to a joint isn’t clear-cut.

“A lot of times the problem is the owner doesn’t know what the joints are or where they are, because the pouches aren’t necessarily where you look at the joints but, sometimes, a little higher up or down,” says Modesto.

“Joints have paths and extensions and pouches that you might not think are related,” says van Harreveld. “If the wound’s in the big picture of the vicinity of the joints, reach out to your ­veterinarian.” 

3. It’s Just a Small Wound

Small wounds might seem a relief at first, but our sources say they’re the most treacherous. Even a 2-millimeter-deep puncture wound from a wire could penetrate the synovial membrane.

Worse, tiny wounds tend to close up quickly, trapping infection inside. “It’s like if you prick an eraser with a ­sewing ­needle,” says van Harreveld. “When you pull it out, you can’t find the hole anymore.”

If bacteria slip in before a wound closes, they create infection; the body’s reaction will be to create more synovial fluid, leading to increasing pressure in a closed space, making the horse very lame. 

4. I’d Better Treat This With Spray/Cream/Solution

Aiming to stave off infection, many owners reach for disinfectant when wounds are near joints. Ironically, however, this isn’t a good move. In particular, it can be harmful to any cartilage that might have gotten exposed in the injury.

“Disinfectants can be very abrasive,” says van Harreveld. “The most important structure in the joint that’s related to arthritis is cartilage, which is very sensitive to different chemicals. If something like iodine solution hits the cartilage, you can have long-lasting effects that could deteriorate that joint long-term.”

The worst, he adds, is hydrogen peroxide. “People get the impression that just because it bubbles up, it’s doing something helpful, but actually it can really desiccate wounds and create more damage.”

5. I’ll Just Let This Air Out

Airing out can be helpful for healing some types of wounds, but it’s critical to keep a joint wound covered. That’s because the goal is to protect the synovial fluid from contaminants in the environment as much as possible.

“Just keep it clean and protected,” says Modesto. Gently wipe or rinse the wound with water, and cover it with a standing wrap or anything else that protects it from dirt until the vet arrives.

Even a clean stall with clean shavings isn’t “clean” enough when the synovial fluid is involved, adds van Harreveld. “All those shavings are going to stick to it, and the bacterial count is going to go up significantly higher,” he says. “It doesn’t need to be a fancy bandage, but keep it covered until we can get there.”

Bleeding under the bandage is not necessarily a bad thing, he explains. Dripping blood can help flush out the wound, and horses can lose several cups of blood without it affecting their health. However, if they’ve cut an artery and/or are hemorrhaging, owners should use pressure bandages (not tourniquets) to control the flow. 

6. Let’s Give Him Bute and See How He Does

Loving owners don’t want their horses suffering, so they might be quick to give a non-steroidal anti-inflammatory drug such as phenylbutazone (Bute) or flunixin meglumine (Banamine) for wound pain relief.

But these drugs can mask early signs of infection, so it’s better to hold off until the veterinarian orders it, says Modesto.

“Bute and Banamine are extremely powerful,” says van Harreveld, so powerful the drugs could interfere with the critical step of lameness evaluation when veterinarians assess joint wounds.

“They could make a horse that would normally be lame from an infection look sound,” he says. “So don’t give any medications until we get there; that will make our diagnostics significantly more accurate.” 

Treatment: Tapping, Flushing, and Broad-Spectrum Antibiotics

Upon arrival, you can expect your veterinarian to carefully inspect the joint, apply pressure to see if it’s leaking, and clean and debride the wound. The exam might also include X rays, ultrasound, and contrast imaging—injection of a contrast medium visible on X ray—to help find leakage, says Modesto. He or she will also make sure the horse’s tetanus vaccine is up to date.

Vets sometimes inject sterile saline into the opposite side of the joint to see if it pushes fluid out of the wound, says van Harreveld. And they can run a white blood cell count (WBC), total protein (TP), and serum amyloid A (SAA) test on the joint fluid to know, within a matter of minutes, to what degree it is infected.

If the wound does leak, veterinarians can try flushing it with large amounts of sterile saline, with the idea of diluting the fluid to eliminate infectious organisms. (Horses replenish the lost synovial fluid rapidly.) However, this usually requires anesthesia to keep the horse calm—­because he could make things worse if he moves during the procedure, necessitating a trip to a referral clinic.

Veterinarians can also take joint fluid samples for analysis and start broad-spectrum antibiotics at the farm right away. One mainstay of therapy, called regional limb perfusion, involves isolating the joint area with tourniquets above and below and injecting antibiotics into the blood vessels. This technique, performed multiple times daily or every other day, delivers the treatment directly to the affected tissues, including the synovial membrane.

In the hospital, surgeons can lavage the synovial capsules thoroughly and then infuse targeted antimicrobials according to culture results on the samples. If all goes well the horse can be on the mend within a couple of days. As SAA levels drop and the horse is comfortable without anti-­inflammatories, he can go home for normal wound care, says van Harreveld.

Complications: Slow Wound Healing, Cartilage Damage, Arthritis

Ideally, veterinarians want to see infections clear up within two days, but some can drag on for weeks, says Modesto. This is more common when the infection is discovered late. As long as there’s an active infection, nothing in the joint will heal. “Your first battle is to minimize that bacterial load,” he says.

Infections can attack the delicate cartilage, which plays a vital role in joint health. And, unfortunately, even when cartilage heals, it’s never quite the same. “It’s always going to be fibrous, granular scar tissue,” says Modesto.

The scar tissue won’t work the same way as the original cartilage, he says. Horses with damaged cartilage develop arthritis in their affected joints, causing chronic pain and affecting performance. The older the horse, the greater his risk of developing arthritis in that joint.

Take-Home Message

The great dichotomy of joint wounds, our sources say, is they usually turn out really great or really terrible. The good news is the prognosis depends almost entirely on something owners can control: the time to veterinary intervention.

“With early treatment, the prognosis is really quite good,” says van Harreveld. “But when treatment starts even a day or two late, that prognosis goes down ­exponentially.”