THE EFFECT OF LIFELONG EXERCISE ON CANINE ARTICULAR-CARTILAGE

The effect of long-term exercise on canine knees was studied to determ ine whether an increased level of lifelong weightbearing exercise caus es degeneration, or changes that may lead to degeneration, of articula r cartilage. Eleven dogs were exercised on a treadmill at 3 km/hr for 75 minutes 5 days a week for 527 weeks while carrying jackets weighing 130% of their body weight. Ten control dogs were allowed unrestricted activity in cages for the 550 weeks. At the completion of the study a ll knee joints were inspected for evidence of joint injury and degener ation. Articular cartilage surfaces from the medial tibial plateau wer e examined by light microscopy, the cartilage thickness was measured, and the intrinsic material properties were determined by mechanical te sting. No joints had ligament or meniscal injuries, cartilage erosions , or osteophytes. Light microscopy did not demonstrate cartilage fibri llation or differences in safranin O staining of the tibial articular cartilages between the two groups. Furthermore, the tibial articular c artilage thickness and mechanical properties did not differ between th e two groups. These results show that a lifetime of regular weightbear ing exercise in dogs with normal joints did not cause alterations in t he structure and mechanical properties of articular cartilage that mig ht lead to joint degeneration.