joint injections

Injecting anti-inflammatories into racehorses’ joints might help them perform to the best of their abilities. But they might also delay detection of serious issues that could worsen if the horse continues to train and race, British researchers have learned. There’s a non-negligible risk of fracture of the treated joint shortly after treatment, their recent study revealed.

“Trainers should be aware that intra-articular (in the joint) medications are a tool with potentially many benefits, but also we need to be careful about selecting the cases receive this treatment,” said Lewis C. R. Smith, BVetMed, CertES(Orth), DESTS, Dipl. ECVS, FRCVS, RCVS, and European Specialist in Equine Surgery, at Rossdales Equine Hospital, in Newmarket, U.K.

Smith and colleagues reviewed the records from all 1,488 flat-racing Thoroughbreds that had received intrasynovial (within a joint, bursa, or tendon sheath) medication by their primary veterinarian in Newmarket from 2006 to 2011. They categorized any fractures, before or up to 56 days after treatment, by location, type, and severity.

In total, the horses received more than 8,500 injections during the study period, Smith said. They identified 96 fractures in treated joints; the researchers considered 44 of those “serious” and 11 were euthanized as a result. However, about half of the horses with fractures eventually returned to racing.

The team said 2-year-olds were more likely to sustain a fracture after their first joint injections than three-year-olds. That finding “would suggest that if 2-year-olds are showing a failure to adapt to training manifest by lameness requiring intrasynovial medication, then they are at higher risk of fracture than older horses,” they reported. “There is a growing body of work that suggests better long-term musculoskeletal health and positive performance outcomes (including career longevity) may ensue from early introduction of exercise.”

However, is the horse is failing to adapt to this exercise as a 2-year-old, it might be better to rest the animal rather than continue training with the aid of joint injections, Smith said.

Still, the study revealed the serious fracture rate after joint injections within the Rossdales clinic of 3%, which is relatively low compared to what other clinics have reported, said Smith. Nonetheless, the risk that bones might be weakening and developing stress fractures remains. And if the related pain is relieved and the horse continues to use the joints as though they were healthy, the added stress could lead to fracture.

“There is a worry that intra-articular injections can mask pain and therefore contribute worsening of pre-existing fissures or cracks in the bone,” Smith said. “Trainers are often under tremendous pressure to have horses running in races, and everyone in the industry has to recognize that getting horses safely and successfully to the track can be more complex than it first appears.”

The U.S. passed regulations a few years ago to control the overuse of joint injections in racehorses, he said. The U.K. also manages the use of these drugs well, but studies such as this one are necessary to “benchmark our performance,” Smith said.

“We believe that indiscriminate use of intra-articular medication could be a factor in why some horses develop fractures and, therefore, it is important to audit your own population of horses,” he said. “Now that we have figures, we can use them to see whether we can prevent more fractures from occurring. As a team at Rossdales, we are constantly striving to provide better care for the horses that we treat.”

Future research should include a control population to analyze fracture rates in untreated horses for comparison, Smith said.

While veterinarians and trainers have been well-meaning in their efforts to relieve the pain in their horses, the study suggests that, in some cases, masking pain does not always work in the horse’s favor, he said.

“I do firmly believe that it is only by analyzing our mistakes that we can hope not to repeat them in the future,” Smith said.

The study, “A longitudinal study of fractures in 1488 Thoroughbred racehorses receiving intrasynovial medication: 2006-2011,” will appear in an upcoming issue of the Equine Veterinary Journal.