Association of C-reactive protein with osteoarthritis: Evidence from a retrospective analysis

Osteoarthritis (OA) is a common chronic inflammatory joint disease that severely affects the quality of life in middle-aged and older adults. C-reactive protein (CRP) is a classical inflammatory biomarker; however, its cross-sectional association with the presence of OA remains unclear. This study aimed to evaluate the association between CRP and other blood markers with prevalent OA in a hospital-based population. A total of 8652 participants were included in this retrospective cross-sectional study. Multivariable logistic regression models were used to assess the association between CRP and OA, and restricted cubic spline regression was applied to examine dose-response relationships. Subgroup analyses were conducted to explore potential heterogeneity of associations. CRP levels were linearly and positively associated with the presence of OA (P < .001), and this association remained statistically significant after multivariable adjustment (odds ratio = 1.013, 95% confidence interval = 1.006-1.021). Restricted cubic spline analysis revealed a linear association between CRP and OA, whereas white blood cell count exhibited a nonlinear pattern. Although statistically significant, the effect size was small, indicating limited clinical relevance at the individual level. In this retrospective cross-sectional study, CRP levels were modestly associated with prevalent OA among hospital-attending adults in China. These findings support an association between systemic inflammation and OA but should be interpreted cautiously given the lack of temporal ordering and potential residual confounding.