To investigate the association between obesity-related metabolic indices and the risk of knee osteoarthritis(KOA) in middle-aged and older Chinese adults(≥45 years) using data from the China Health and Retirement Longitudinal Study(CHARLS).

Data from two CHARLS survey waves(2011—2012 and 2015—2016) were analyzed. Obesity indices—including body mass index(BMI), waist circumference(WC), waist-to-height ratio(WHtR), visceral adiposity index(VAI), a body shape index(ABSI), body roundness index(BRI), lipid accumulation product(LAP), conicity index(CI), and Chinese visceral adiposity index(CVAI)-and metabolic indices-triglyceride glucose index(TyG), TyG-BMI, TyG-WC, and TyG-WHtR-were collected. Covariates comprised demographic characteristics, lifestyle factors, and health status. Three multivariate logistic regression models were constructed. Sex-subgroup analyses assessed heterogeneity, and receiver operating characteristic(ROC) curves with area under the curve(AUC) were used to evaluate diagnostic performance.

Among 9527 participants, the prevalence of KOA was 9.59%(914/9527). After adjusting for confounders, linear regression revealed significant positive associations between KOA and BMI(OR=1.02, 95% CI: 1.00-1.04, P=0.048), BRI(OR=1.06, 95% CI: 1.01-1.13, P=0.030), LAP(OR=1.03, 95% CI: 1.00-1.05, P=0.020), TyG-BMI(OR=1.02, 95% CI: 1.00-1.05, P=0.020), and TyG-WHtR(OR=1.13, 95% CI: 1.02-1.25, P=0.020). Sex-stratified analyses showed that in women, BMI(OR=1.03, 95% CI: 1.01-1.06, P=0.020), WHtR(OR=1.18, 95% CI: 1.02-1.36, P=0.020), BRI(OR=1.08, 95% CI: 1.01-1.16, P=0.020), LAP(OR=1.03, 95% CI: 1.01-1.06, P=0.020), CVAI(OR=1.04, 95% CI: 1.01-1.07, P=0.009), TyG-BMI(OR=1.03, 95% CI: 1.01-1.06, P=0.006), TyG-WC(OR=1.10, 95% CI: 1.01-1.19, P=0.02), and TyG-WHtR(OR=1.18, 95% CI: 1.04-1.34, P=0.010) were positively associated with KOA, whereas no significant associations were observed in men(P > 0.05 for all indices). Significant sex interactions were found for WC(P=0.010), CVAI(P=0.002), and TyG-WC(P=0.020). ROC analysis indicated limited diagnostic utility for all indices[BRI(AUC=0.547, 95% CI: 0.526-0.567), TyG-WHtR(AUC=0.544, 95% CI: 0.524-0.564), others ≤0.530].

BMI, BRI, LAP, TyG-BMI, and TyG-WHtR may serve as auxiliary indicators for KOA risk assessment in middle-aged and older women, but their standalone screening value remains modest. Clinical evaluation and integration with other risk factors are recommended for comprehensive risk stratification.