Prevalence and risk factors of knee osteoarthritis in Huang-Pu District, Shanghai, China

Objectives: A community-based survey on the prevalence of knee osteoarthritis (OA) and associated factors was carried out in Shanghai, People's Republic of China. Methods: Of 2,305 registered residents >= 40 years of age, 2,093 were examined by interview and questionnaire. One hundred ninety knee pain-positive and 510 knee pain-negative subjects received radiography. Results: Radiographic knee OA (RKOA) was found in 72.1% (137/190) of symptomatic and 41.6% (212/510) of asymptomatic subjects (SKOA and AsKOA, respectively). The estimated prevalences of symptomatic and asymptomatic knee OA in the community were 7.2% and 37.4%, respectively. Women had higher SKOA prevalence than men (9.8% vs 3.7%, P < 0.01). Compared with Caucasians, the urban Shanghai population had a higher prevalence of tibiofemoral joint OA. Conclusions: There was a higher proportion of SKOA than AsKOA (72.1% vs 41.6%), and SKOA was significantly more associated with disability (81.0% vs 26.9%, P < 0.01). The prevalence of SKOA increased with age, from 1.3% in the 40-49-year-old age group to 13.2% in the 70+ group. Age, body mass index, and female gender were associated risk factors for knee OA.