Body Composition in Individuals with Asymptomatic Osteoarthritis of the Knee

Greater body mass index (BMI) is associated with a greater risk of osteoarthritis (OA). This study sought to investigate whether the association is mediated by fat mass or lean mass. The study involved 170 men and 488 women aged between 20 and 90 (average age: 55) who were randomly recruited from Ho Chi Minh City, Vietnam. The presence of knee OA was radiographically diagnosed based on the Kellgren-Lawrence criteria. Lean mass (LM) and fat mass (FM) were obtained from the DXA whole body scan (Hologic QDR-4500). The relationship between OA, LM, and FM was analyzed by a series of multiple linear regression models which take into account the effects of gender and age. As expected, men and women with knee OA were older than those without OA (65 vs 51 year in men, and 64 vs 52 year in women). After adjusting for age, OA was associated with greater FM and percent body fat (PBF), but the association was only observed in women, not in men. There was no statistically significant difference in LM between OA and non-OA individuals. Moreover, after adjusting for age and BMI or PBF, bone density in OA patients was not significantly different from non-OA individuals. Women with OA of the knee have greater fat mass than non-OA individuals, and that there is no significant difference in bone density between OA and non-OA individuals. Thus, the association between body mass index and OA is mainly mediated by fat mass.