A prospective cohort study involving 5003 participants from the Rotterdam Study (1996-2009) investigated the association between weight-bearing and non-weight-bearing recreational physical activities and the risk of knee osteoarthritis. The study found that higher weight-bearing activity was significantly associated with an increased risk of incident knee osteoarthritis, particularly among individuals with low lower-limb muscle mass (LMI). In contrast, non-weight-bearing activity did not show a significant association. The association between weight-bearing activity and knee osteoarthritis was observed only in the lowest LMI tertile, but not in the middle or high LMI tertiles. The study also found that weight-bearing activity was significantly associated with incident radiographic knee osteoarthritis in the lowest LMI tertile, but not in other tertiles after adjusting for confounders. The study suggests that weight-bearing activity may increase the risk of knee osteoarthritis in individuals with low lower-limb muscle mass, highlighting the importance of considering muscle mass when recommending physical activity. The study also found that physical activity levels were not significantly associated with symptomatic knee osteoarthritis. The study's findings suggest that tailored physical activity recommendations based on muscle mass and osteoarthritis risk could help optimize the benefits of physical activity while minimizing the risk of developing osteoarthritis. The study has limitations, including potential recall bias and the lack of data on knee injury. The study is embedded in the Rotterdam Study, a large, deeply phenotyped prospective cohort study. The study's results suggest that weight-bearing activity may increase the risk of knee osteoarthritis in individuals with low lower-limb muscle mass, and that physical activity should be tailored to individual muscle mass and osteoarthritis risk. The study provides evidence for future tailored physical activity recommendations based on a person's muscle mass and osteoarthritis risk, which can help optimize the benefits of physical activity while minimizing the potential risk of developing osteoarthritis.A prospective cohort study involving 5003 participants from the Rotterdam Study (1996-2009) investigated the association between weight-bearing and non-weight-bearing recreational physical activities and the risk of knee osteoarthritis. The study found that higher weight-bearing activity was significantly associated with an increased risk of incident knee osteoarthritis, particularly among individuals with low lower-limb muscle mass (LMI). In contrast, non-weight-bearing activity did not show a significant association. The association between weight-bearing activity and knee osteoarthritis was observed only in the lowest LMI tertile, but not in the middle or high LMI tertiles. The study also found that weight-bearing activity was significantly associated with incident radiographic knee osteoarthritis in the lowest LMI tertile, but not in other tertiles after adjusting for confounders. The study suggests that weight-bearing activity may increase the risk of knee osteoarthritis in individuals with low lower-limb muscle mass, highlighting the importance of considering muscle mass when recommending physical activity. The study also found that physical activity levels were not significantly associated with symptomatic knee osteoarthritis. The study's findings suggest that tailored physical activity recommendations based on muscle mass and osteoarthritis risk could help optimize the benefits of physical activity while minimizing the risk of developing osteoarthritis. The study has limitations, including potential recall bias and the lack of data on knee injury. The study is embedded in the Rotterdam Study, a large, deeply phenotyped prospective cohort study. The study's results suggest that weight-bearing activity may increase the risk of knee osteoarthritis in individuals with low lower-limb muscle mass, and that physical activity should be tailored to individual muscle mass and osteoarthritis risk. The study provides evidence for future tailored physical activity recommendations based on a person's muscle mass and osteoarthritis risk, which can help optimize the benefits of physical activity while minimizing the potential risk of developing osteoarthritis.