Objective: To estimate the prevalence of radiographic and symptomatic knee osteoarthritis (OA) in a remote rural region of northern China, and compare them with those reported in Beijing and with data from the Framingham (Massachusetts) cohort.
Methods: A population-based cross-sectional survey was conducted among 1,030 residents of Wuchuan County, Inner Mongolia, age > or =50 years. Survey participants, mostly farmers reporting heavy physical occupational activity, completed an interviewer-based questionnaire, and bilateral weight-bearing posteroanterior semiflexed knee radiographs were obtained.
Results: Whereas the overall prevalence of radiographic knee OA was similar to that demonstrated in the Beijing OA study, men in Wuchuan had approximately double the prevalence of severe radiographic knee OA (prevalence ratio [PR] 2.5, 95% confidence interval [95% CI] 1.6-3.8) and symptomatic knee OA (PR 1.9, 95% CI 1.3-2.9). Women in Wuchuan also had a higher prevalence of both severe radiographic (PR 1.4, 95% CI 1.0-2.0) and symptomatic knee OA (PR 1.6, 95% CI 1.2-2.1) compared with their Beijing counterparts. The prevalence of bilateral OA and lateral compartment disease were 2-3 times higher in both Chinese cohorts compared with estimates from the Framingham OA study.
Conclusion: The prevalence of symptomatic knee OA in rural areas of China is much higher than reported from urban regions of China or in the Framingham cohort. The higher representation of bilateral and lateral compartment disease in China suggests a unique phenotype to OA. These findings will be useful for guiding the distribution of future health care resources and preventive strategies.