Pathologic findings and pathogenesis of racetrack injuries.

Many lesions of the musculoskeletal system of racing horses are either acute traumatic lesions or are chronic biomechanically induced lesions that become suddenly unstable and provoke acute clinical signs. The latter lesions along with those of DJD are much more common and are of much greater overall economic importance to the racing industry than are the acute traumatic injuries. Chronic biomechanical lesions occur at predictable sites and are the result of an imbalance between repetitive microtrauma sustained in athletic performance and adaptive repair mechanisms of skeletal tissues. The distribution of these lesions in the limbs reflects the patterns of biomechanical forces placed on the skeleton during work at racing speeds and, therefore, reflects the type of racing activity for which the horse was bred. Lesions result when there is a failure of the stressed skeletal structures to adapt to the biomechanical forces placed upon them. Rest or a reduction in the level of training activity permit the healing of many asymptomatic and presumably some symptomatic lesions of the bony tissues. Articular cartilage, tendons, and ligaments have a lower capacity to resolve the damage and return to normal structure and function.