Purpose: The present study aims to estimate the prevalence of symptomatic knee osteoarthritis (OA) and analyze the correlation between symptomatic knee osteoarthritis and complete blood count (CBC) Results through large sample data from multiple centers in China. Methods: Nationally representative sample was derived from China Health and Retirement Longitudinal Study (CHARLS), a national random sample of the Chinese population, wave 3, which was mainly completed in 2015. A total of 21,100 individuals were interviewed, blood samples from 13,420 individuals were collected then. Individuals were asked whether they were often troubled with pain, after that, they’ll be asked to point out the site(s) of the body where he or she was currently experiencing pain, knee part included. At the same time, each individual was asked if he or she had a doctor-diagnosed arthritis. We define a subject as a symptomatic knee OA if he or she responded both questions positively. After data cleaning, a number of 12,952 individuals were categorized into four groups: (1) group 1: symptomatic knee OA individuals, (2) group 2: individuals who are suffering from knee pain but have no arthritis, (3) group 3: individuals who are diagnosed with arthritis but have no knee pain, (4) group 4: individuals without arthritis and knee pain. The flow chart of this study was shown in Figure 1. Post hoc multiple comparisons were conducted to analyze the CBC (hemoglobin, hematocrit, white blood cell count, platelet counts and mean corpuscular volume included) level in different groups. The criterion of significance is p < 0.05. Results: Among the 20,967 individuals included in the analysis, 19,692 answered both the knee pain and the doctor-diagnosed arthritis question, the prevalence of symptomatic knee OA was 9.18% (1,808 individuals). The CBC level (WBC, HGB, HCT, MCV, PLT) of the four groups was shown in Table 1 and Figure 2. Statistics showed that the hemoglobin level of symptomatic knee OA individuals (13.34±1.80 g/dL) was lower than that of other individuals (group 2 to 4: 13.51±1.98 g/dL, 13.62±2.03 g/dL, 13.82±1.92 g/dL, respectively), and the difference was statistically significant. The hematocrit level of symptomatic knee OA individuals (40.53±5.32 %) was lower than that of other individuals (group 2 to 4: 40.64±5.84 %, 41.23±5.83 %, 41.80±5.62 %, respectively), and the difference was statistically significant. The platelet counts level in arthritis individuals without knee pain was the lowest (199.09±76.88 ×109/L) when compared to other groups (group 1: 203.84±74.05 ×109/L, group 2: 208.21±81.03 ×109/L, group 4: 207.33±74.81 ×109/L). The level of white blood cell count and mean corpuscular volume showed no significance between the four groups. The significance between CBC level in the four groups was shown in Table 2. Conclusions: Symptomatic knee OA in China was still prevalent, the prevalence of symptomatic knee OA in 2015 was higher than that in 2011. Individuals with symptomatic knee OA had a tendency to lower hemoglobin and hematocrit, future research should pay more attention to effective treatment, management and prevention of symptomatic knee OA.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)