EDITOR’S NOTE: The information, ideas and opinions expressed are those of the author and do not necessarily represent those of the United States Department of Agriculture.

Veterinarians in Melbourne, Australia, examined the relationship between fetlock injury identified by increased radiopharmaceutical uptake on nuclear scintigraphic (bone scan) images of the palmar/plantar regions of the distal condyles of the cannon bones and the solar angles of the hooves of Thoroughbred racehorses in training. The horses were among those presented to a university veterinary hospital for evaluation of poor performance or lameness over a nine year period. A total of 359 horses were included in the study. Following scoring of the nuclear uptake (hot spots) solar angles were categorized as positive (heel higher than toe), neutral (sole parallel to ground surface) or negative (toe higher than heel). Performance data were also obtained from a commercial database and evaluated.

About half the horses (52%) were classified as having a positive solar angle on the forelimbs with 34% having a neutral angle and 14% having a negative angle. Conversely, a negative solar angle was most common (60%) in the hind limbs with 26% of horses having a neutral angle and only 14% having a positive angle.

Horses with neutral or negative solar angles, horses that were older when examined and those with higher earnings per start were more likely to have moderate or marked forelimb nuclear uptake indicating injury to the fetlock. For the hind limbs, increased nuclear uptake was also associated with a negative…