LIFELONG MODERATE RUNNING TRAINING INCREASES THE INCIDENCE AND SEVERITY OF OSTEOARTHRITIS IN THE KNEE-JOINT OF C57BL MICE

Background: Inbred C57BL male mice express a high incidence of spontan eous osteoarthritis of the knee joint at the age of 18 months. We used this strain of mice to find out the effects of life-long, moderate ru nning exercise on the health of articular cartilage and the incidence of osteoarthritis. Methods: Male mice (294) were divided into controls and runners. The runners were trained daily between 2 and 18 months o f age. The speed was 13.3 m/min and the distance on a flatbelt treadmi ll was 1,000 m/day. The mice were sacrificed at the ages of 2, 6, 10, 14, and 18 months. The knee joints were sectioned in frontal direction and the osteoarthritic changes were graded using a conventional light microscope. The reproducibility of the grading method was tested by c alculating the extended K-coefficient for the results of six researche rs. Results: The incidence of osteoarthritis at the age of 18 months i ncreased from 72% in controls to 88% in runners in the medial tibial c ondyles (P < 0.05), and from 80 to 96% in the lateral tibial condyles (P < 0.001). The incidence of the most severe osteoarthritic changes r ose from 16% in controls to 36% in runners in the medial tibial condyl es, and from 4 to 36% in the lateral tibial condyles. Conclusion: Acco rding to our results, the moderate, long-lasting running exercise acce lerates the development of osteoarthritis in the knee joints of C57BL mice. (C) 1995 Wiley-Liss, Inc.