Most horse owners are familiar with a typical lameness exam: The veterinarian observes the horse trotting briskly in a straight line, watching for signs of uneven movement. But if the patient is harboring a mild lameness, that brisk trot could be masking clinical signs, according to British researchers, whose recent study results indicate that evaluating milder forms of lameness in a straight-line trot could be more accurate when the handler keeps the speed down.

“Our study suggests that in sound to mildly lame horses, movement asymmetry (as measured objectively with equipment) doesn’t actually change much, if at all, when the horse is trotting fast on the straight,” said Sandra Starke, PhD candidate, researcher in the Department of Veterinary Clinical Sciences at the Royal Veterinary College, in Hatfield, UK. “However, more horses were judged sound at faster speeds when they were evaluated subjectively (visual examination). So it is possible that the horses are just going too fast for the asymmetry to be seen."

Starke and her colleagues evaluated 10 horses—ranging from sound to mildly lame in either the front or hind legs—as they trotted at slow, normal (“preferred”), and fast speeds, in both straight lines and circles. The researchers asked six experienced equine clinicians to evaluate these horses for lameness. Meanwhile, the team fitted the horses with sensors for an objective evaluation of asymmetry.

On a straight line, the practitioners judged more horses to be sound at the fast trot than at the other speeds; by contrast, the greatest number of mild lameness detections occurred at the slow trot. Even so, objective measurements still showed asymmetry at the fast trot in horses that had been determined sound by the observers, Starke said