Background: Runners and team players frequently use motorized treadmill to impose exercise stress. On the other hand, some studies showed that running may lead to knee osteoarthritis (OA). The current study aimed at comparing the effects of running on inclined treadmill on the occurrence of knee joint OA between male and female rats with the same age and body weight. Methods: Forty adult male and female Wistar rats were randomly and equally divided into two male and female control and two male and female runner groups. A similar running exercise was performed in both male and female rats for six weeks on a treadmill with 18°inclination. On the day 43, animals were euthanized and the whole rat knee joints were evaluated microscopically and macroscopically. Results: The gross evaluation of knee articular surface in four male and all female runner rats were irregular. Mankin's findings were higher in the female runners than the male runners. In female runners, the synovial layer showed a mild sinovitis. The average of cartilage thickness and chondrocyte number were significantly lower in female runner group than the female controls. Conclusions:The obtained results showed no sinovitis and moderate sinovitis in male and female runners, respectively. There was mild OA both in male and female runners. The current study confirmed that the development of knee OA may be related to the gender differences.

Exercise has been shown to be beneficial to the skeleton, in both humans and animals. This study was done to test the sex-related difference in the risk of OA (osteoarthritis) of the knee joint and also on the subchondral bone after moderate running exercise.Forty male and female Wistar rats were randomly assigned to four equal groups (2 male and 2 female groups) in a same condition. Ten of each sex were selected as control groups, while running exercises were performed in remained 20 male and female rats using a motor treadmill to motivate rats to run daily distances of 1 km at 5 days/week within six weeks.On day 43, all animals were sacrificed and the knee articular cartilage and also histomorphometric parameters of subchondral bone and mid shaft of tibia were evaluated.Results showed mild OA in both male and female runner groups. Results in male runner rats were significantly lesser than that in female runners. On the other hand, the difference 2 in female runner group showed significant changes in comparison with other groups in histomorphometric parameters in tibia.Obtained results showed that the development of knee OA and subchondral bone changes may be related to the sex differences. Although there was no synovitis in male runners but female runner group showed mild hyperemia dropsy with a moderate synovitis in this region.