The high prevalence of knee osteoarthritis in a rural Wuchuan population

Objective To estimate the prevalence of radiographic and symptomatic knee osteoarthritis (OA) in a remote rural region of northern China (Wuchuan County, Inner Mongolia) and compare these with those reported in Beijing and data from the Framingham (Massachusetts, USA) cohort. Methods A population-based cross sectional survey was conducted among 1025 residents of Wuchuan County, Inner Mongolia, aged 50 years and over. Survey participants, mostly farmers reporting heavy physical occupational activity, completed an interviewer based questionnaire and obtained bilateral weight-bearing posterior-anterior semi-flexed knee radiographs. Results While the prevalence of radiographic knee OA was similar to that demonstrated in the Beijing OA study, the prevalence of severe radiographic [prevalence ratio (PR) 2.48, 95%CI(1.62, 3.78)] and symptomatic knee OA [PR 1.91, 95%CI(1.25, 2.91)] in men in Wuchuan were higher than ones in Beijing. Women in Wuchuan also had a higher prevalence of both severe radiographic [PR 1.42, 95%CKI (1.03, 1.97)] and symptomatic knee OA [PR 1.55, 95%CI(1.17, 2.05)] compared with their Beijing counterparts. The prevalence of bilateral OA and lateral compartment OA were two to three 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 Wuehuan is much higher than that reported from urban regions of China (Beijing) or in the Framingham cohort. The higher representation of bilateral and lateral compartment OA in China suggests a unique phenotype to OA. The findings will be useful to guide the distribution of future health care resources and preventive strategies. Key words: Osteoarthritis; knee; Prevalence; Cross-sectional studies