Musculoskeletal injury is the most common cause of lost training days for Thoroughbred racehorses. This type of injury, particularly fractures, is also cited as a major reason horses leave the industry. But the incidence and characteristics of fractures in racing Thoroughbreds are not well understood.

Characterizing fractures was the aim of Kristien Verheyen, DVM, MSc, and James Wood, BSc, BVetMed, MSc, PhD, of the Animal Health Trust in the United Kingdom. These researchers set out to determine the incidence of fractures in British Thoroughbreds in race training and to describe the fracture types seen.

Due to the high level of cooperation required for this two-year study, 13 trainers were chosen on recommendations from veterinarians, rather than a typical random sample. A total of 1,178 horses were monitored daily, including their exercise regimens and any fracture occurrence. This provided 12,893 months of data, which was analyzed as the number of horses at risk of fracture per month, or “horse months.”

Fractures totaled 148, a rate of 1.15 per 100 horse months. The majority of fractures (78%) occurred during training, not racing. Verheyen explains, “It is likely that the majority of fractures occurred during training because horses spend much more time training than racing. When you take time at risk into account, the fracture rate is actually 20 times higher in racing than training