Many horses can be off in their performance, yet not show clinical signs of lameness. There might be no answers after the customary diagnostic work-up, leaving veterinarian and owner scratching their heads and looking for the next stop in the quest for a diagnosis.

Carl Kirker-Head, MRCVS, Dipl. ACVS, Marilyn M. Simpson Chair in Equine Medicine of Tufts University School of Veterinary Medicine, explained the phenomenon of subtle or obscure lameness as one that is difficult to see or define consistently.

“Subtle lameness, to each of us, might be a different thing in terms of its severity and presentation,” he said. “The lameness might appear to switch from one leg to another; it may come, it may go. The horse who is ‘off ‘ is just marginally unsound and frequently doesn’t respond to the usual course of treatment.”

Exploring an obscure lameness can be expensive, inconclusive, and trying, and is not always appropriate. Patience on the part of the owner and veterinarian are key, along with the understanding that even if the cause of the mysterious lameness is found, it isn’t guaranteed to respond to treatment. However, many times it proves worthwhile, as in the following case.

Sitting on the desk of Jay Merriam, DVM, at his Massachusetts Equine Clinic in Uxbridge is a photo of a black dressage horse. The picture is signed by the rider, “Thanks for the trip to Barcelona.”

At 13, the horse was considered too old to send to the Olympics by his trainer. The warmblood’s condition exemplified Merriam’s description of subtle lameness–a horse previously capable of working at a certain level no longer performing up to par. “It’s lameness more noticed by the rider than by the visible eye,” Merriam said.

The horse was sent to Merriam because of chronic underperformance as an FEI-level dressage horse. He had been diagnosed with