Osteochondrosis—one of the most common forms of developmental orthopedic disease—in young Thoroughbreds can be directly linked to racing performance later in life, according to recent study results from a team of French equine orthopedics authorities.

The researchers found that the type and location of juvenile osteochondral condition (JOCC) lesions can affect when those horses race, how well they race, how long they’ll race, and if they’ll even end up racing at all, said Céline Robert, PhD, DVM, lecturer and researcher at the French National Veterinary School of Alfort in Maisons-Alfort. The lesions’ effect on performance is closely linked to their number and severity, Robert warned.

“Buyers (and especially advising veterinarians) should take into consideration not only the number of visible lesions in all radiographic images but also the severity of those lesions,” she said. “A single, isolated lesion that’s not very severe will probably have no influence on the horse’s career. By contrast, however, a serious lesion or the presence of several lesions could limit the horse’s career.”

Robert and colleagues followed the racing performances of 328 Thoroughbreds radiographed as yearlings; They found that those horses with the most JOCC lesions and those with the most severe JOCC lesions tended to start racing late, stop racing early, or not race at all, Robert said.

Lesions in the carpus joint (or knee)—which is a common site for racing injuries in Thoroughbreds—were a risk factor for not racing as a 2-year-old, but not as a 3-year-old, she said. “