“We do believe that parenteral medications do prolong the time period before normal wear and tear catches up to you,” he added. “It’s like saying ‘Can I get more tread life out of my tires if I drive this way?’ ‘If I give my horse Legend, can I go longer before I have to inject a joint?’ There’s some evidence that suggests that that is true, but that’s not been proven definitively.”
If Markell had a client with a limited budget and a horse showing subtle signs of degenerative joint disease, but without lameness, he would recommend a parenteral medication such as Adequan or Legend.
“If I could only pick one, I’d pick injectibles, because there’s been more solid research on them,” he said.
Intra-Articular Injections: The Gold Standard
So when do you escalate your battle against joint disease from oral supplements and parenteral medications to the level of intra-articular injections? When your horse has a diagnosed disease process in a joint or multiple joints that’s causing lameness or interfering with performance.
“If you have a horse that has a particular joint that hurts, the best thing to do is to treat that particular joint. The analogy is that if you have a fire that’s starting in a trash bin in a parking lot, don’t sprinkle water all over the parking lot to extinguish it. Dump water just in the trash bin. It will put the fire out quicker and more effectively,” said Frisbie.
“If you have inflammation which translates to pain, then decreasing the inflammation decreases the progression of disease. I think people will agree that the most potent way to do it is to treat the joint directly,” he continued.
“Joint injections do what Adequan and Legend do in a more concentrated and direct form,” said Markell. “The idea is that you’re stopping inflammation. That’s really what it’s all about.”
There are many products that veterinarians can inject directly into a joint to decrease inflammation and heal the joint. Hyaluronic acid, as a lubricant to normalize the synovial fluid, and cortisone, a corticosteroid that decreases inflammation, are two popular intra-articular treatments and frequently used in conjunction with one another.
“Cortisone is the body’s natural anti-inflammatory. Studies have shown that if you have two inflamed joints, and you treat one with cortisone once and do nothing to the other one, the horses that have been treated with a specific cortisone have less joint cartilage damage than those that have nothing done. The cortisone put the fire out,” Markell said.
But cortisone doesn’t heal the joint. If the joint requires treatment with cortisone frequently, then the degenerative process is so severe that damage may result with continued stress on the joint.
“You’re not fixing a joint by putting cortisone into it. But by stopping the inflammatory process, you’re lessening further damage to the cartilage,” Markell said.
Medications such as hyaluronic acid and polysulfated glycosaminoglycan can help the joint heal and regenerate cartilage, as can a number of new joint therapies.
Advances in regenerative medicine have brought stem cells, interleukin receptor antagonist protein (IRAP) and platelet-rich plasma (PRP) to the table as intra-articular treatments. These products have added to the veterinarian’s toolbox for treating joint disease.
“Every day I see cases that just a few years ago would have been career-ending injuries and lamenesses,” said Markell. “These therapies are very exciting.”
Frisbie notes that expanding the treatment options has enabled veterinarians to gain headway in frustrating cases of joint disease. “There are different pathways of inflammation and different pathways of pain,” Frisbie said.
“We know that corticosteroids don’t act specifically on the exact same pathway as a product like IRAP, which would make one indicated in one situation and the other in another situation,” Frisbie continued. “If there are horses that responded great to steroids and then they stop responding, maybe you switch to IRAP, and they go back to great response. But there’s no great Venn diagram with trees that you just check off and know you’re right in the end. We know a little bit about the differences in these medications and how they act, but we don’t know everything.”