Background: Sarcopenic obesity (SO) and osteoarthritis (OA) are highly prevalent musculoskeletal conditions that significantly impair health-related quality of life.

Aim: This study investigated the association between SO and OA, and explored the potential mediating role of insulin resistance in this relationship. We utilized data from the National Health and Nutrition Examination Survey (NHANES) 1999-2018.

Methods: This cross-sectional analysis employs NHANES data collected from 1999 to 2018, including participants aged 18 years and older. SO was assessed using dual-energy X-ray absorptiometry (DXA) measurements. Insulin resistance was estimated using the triglyceride-glucose (TyG) index. OA status was based on self-reported physician diagnosis. Statistical analyses included weighted logistic regression, restricted cubic spline (RCS) interaction analysis, mediation analysis using structural equation modeling (SEM), and receiver operating characteristic (ROC) curve analysis. Subgroup analyses were conducted based on age, sex, and diabetes status.

Results: The sarcopenic obese group demonstrated the highest prevalence of OA (23.4 %), hypertension (47.8 %), and diabetes (12.0 %). Additionally, they exhibited elevated levels of triglycerides, cholesterol, glucose, blood urea nitrogen (BUN), creatinine, and uric acid. Logistic regression revealed significant positive associations between sarcopenic obesity, the TyG index, and OA risk. RCS analysis identified significant non-linear relationships and interactions of the TyG index with age, sex, and diabetes status on OA risk. Mediation analysis indicated that the TyG index mediated approximately 4.9 % of the effect of sarcopenic obesity on OA risk. ROC curve analysis demonstrated moderate diagnostic accuracy for the TyG index (AUC = 0.65), which improved when incorporated into the multivariate model (AUC = 0.78). Subgroup analyses confirmed significant associations between the TyG index and sarcopenic obesity with OA risk across different age, sex, and diabetes status categories.

Conclusion: Our findings suggest a significant correlation between insulin resistance, as measured by the TyG index, and elevated OA risk in individuals with sarcopenic obesity. Targeting insulin resistance through future research may be a promising avenue to lower OA risk in this population.