This study aimed to investigate the associations between body mass index (BMI), physical activity levels (PALs) and sociodemographic factors (gender, age, education and marital status) with different outcomes (symptoms) of osteoarthritis (OA) severity, in patients with knee OA.

Cross-sectional study.

The sample included 200 participants from southern Bosnia and Herzegovina (61 males, 65.1±9.01 years of age) who had been diagnosed with primary knee OA.

OA symptoms as evidenced by the Western Ontario and McMaster Universities OA Index (WOMAC) scale, including three subscores (WOMAC-pain, WOMAC-stiffness, WOMAC-functionality) and total WOMAC score. The predictors included age (in years), gender (male or female), BMI, PAL, education level, urban/rural living environment and marital status (partnership).

Female gender was correlated with the WOMAC-pain, WOMAC-stiffness and WOMAC-total. Older age was correlated with the WOMAC-pain and WOMAC-total. Patients who were better educated and reported higher PAL had better WOMAC functionality. BMI was the most significant factor of influence, with higher WOMAC-pain (OR 1.44, 95% CI 1.27 to 1.65), WOMAC-stiffness (OR 1.20, 95% CI 1.1 to –1.33), WOMAC-functionality (OR 1.26, 95% CI 1.13 to 1.40) and WOMAC-total (OR 1.29, 95% CI 1.6 to –1.44) scores in patients with higher BMI.

Results indicate the necessity of controlling body weight in patients with diagnosed knee OA irrespective of gender. Further prospective studies are warranted in order to establish causality between variables.