Effect of physical activity on articular knee joint structures in community-based adults

Objective. It is unclear whether physical activity that is beneficial for the cardiovascular system is detrimental to knee structures. We examined the association between intensity, frequency, and duration of physical activity and knee structures in a community-based population. Methods. A total of 297 healthy adults ages 50-79 years with no history of knee injury or disease were recruited from an existing study on healthy aging. Each subject underwent knee magnetic resonance imaging (MRI) to measure tibial cartilage volume, tibiofemoral cartilage defects, and bone marrow lesions. Physical activity and anthropometric data were obtained via questionnaire during 1990-1994 and 2003-2004. Results. Tibial cartilage volume increased with frequency (P = 0.01) and duration (P = 0.001) of vigorous activity (activity leading to diaphoresis or dyspnea) reported 10 years previously, as well as recent vigorous activity in the 7 days prior to MRI (P = 0.05). Recent weight-bearing vigorous activity increased with tibial cartilage volume (P = 0.02) and was inversely associated with cartilage defects (P = 0.02). A reduced risk of bone marrow lesions was associated with regular walking (P = 0.04). Conclusion. Vigorous physical activity appears to have a beneficial effect on knee articular cartilage in healthy, community-based adults with no history of knee injury or disease. Regular walking reduces the risk of bone marrow lesions in the knee. This study provides further support for a beneficial effect of physical activity for diseases associated with aging and suggests that exercise that is good for the heart is also good for the knees.