This study aimed to investigate the association of self-reported weight change and physical activity with the level of knee pain and health-related quality of life in East Asian women with knee osteoarthritis using population-based data.

A total of 564 women (mean age, 68.2 years, standard deviation, 8.9 years) aged 50 years or older with knee osteoarthritis (Kellgren-Lawrence (K-L) grade ≥ 2) were included in the data analyses from the fifth Korea National Health and Nutrition Examination Survey. Data regarding the radiographic grade, self-reported weight change during the past year, physical activity, level of knee pain, and health-related quality of life (EuroQOL five-dimension (EQ-5D) index) were collected. Multiple regression analysis was performed to identify factors significantly associated with the level of knee pain and health-related quality of life in subgroups according to the body mass index (BMI) range (≤ 22.5, between 22.6 and 27.5, and > 27.5 kg/m²).

In the whole group, the level of knee pain was significantly associated with K-L grade (P < 0.001), and EQ-5D was negatively associated with age (P < 0.001), the level of knee pain (P < 0.001), and weekly hours of vigorous-intensity activity (P = 0.026). In the subgroup analysis, weight gain showed significant association with the level of knee pain only in women with 22.5 kg/m² < BMI ≤ 27.5 kg/m² (P = 0.006). Weight gain showed significant association with EQ-5D in women with BMI ≤ 22.5 kg/m² (P = 0.047) whereas weekly hours of moderate-intensity activity was negatively associated with EQ-5D in women with BMI > 27.5 kg/m².

The association of weight change and physical activity with knee pain and health-related quality of life might be different according to BMI ranges. Well-designed interventions to improve both knee pain and health-related quality of life need to be investigated in future studies that would strictly control physical activity, diet, and weight changes.