Analysis of acute mechanical insult in an animal model of post-traumatic osteoarthrosis

Chronic degeneration of articular cartilage and bone in a rabbit model of p osttraumatic osteoarthrosis has been hypothesized to occur due to acute str esses that exceed a threshold for injury. In this study, we impacted the ra bbit patellofemoral joint at low and high intensities. High-intensity impac ts produced degenerative changes in the joint. such as softening of retropa tellar cartilage, as measured bq indentation, an increase in histopathology of the cartilage, and an increase in thickness of subchondral bone underly ing the cartilage. Low-intensity impacts did not cause these progressive ch anges. These data suggest that low-intensity impacts produced acute tissue stresses below the injury threshold, while high-intensity impacts produced stresses that exceeded the threshold for disease pathogenesis. This study b egins to identify ''safe'' and ''unsafe'' ranges of acute tissue stress, us ing the rabbit patella, which may have future utility in the design of inju ry prevention devices for the human.