Metabolic syndrome and the incidence of knee osteoarthritis: A meta-analysis of prospective cohort studies

Background: Cross-sectional studies suggest an association between metabolic syndrome (MetS) and knee osteoarthritis (KOA). We performed a meta-analysis to evaluate whether MetS is an independent risk factor for KOA. Methods: Prospective cohort studies evaluating the association between MetS and KOA in general population were retrieved from PubMed and Embase. Only studies with multivariate analyses were included. Data were pooled with a random-effect model, which is considered to incorporate heterogeneity among the included studies. Results: Five studies including 94,965 participants were included, with 18,990 people with MetS (20.0%). With a mean follow-up duration of 14.5 years, 2,447 KOA cases occurred. Pooled results showed that MetS was not significant associated with an increased risk of KOA after controlling of factors including body mass index (adjusted risk ratio [RR]: 1.06, 95% CI: 0.92~1.23, p = 0.40; I2 = 33%). Subgroup analysis showed that MetS was independently associated with an increased risk of severe KOA that needed total knee arthroplasty (RR = 1.16, 95% CI: 1.03~1.30, p = 0.02), but not total symptomatic KOA (RR = 0.84, 95% CI: 0.65~1.08, p = 0.18). Stratified analyses suggested that MetS was independently associated with an increased risk of KOA in women (RR = 1.23, 95% CI: 1.03~1.47, p = 0.02), but not in men (RR = 0.90, 95% CI: 0.70~1.14, p = 0.37). Conclusions: Current evidence from prospective cohort studies did not support MetS was an independent risk factor of overall KOA in general population. However, MetS may be associated with an increased risk of severe KOA in general population, or overall KOA risk in women.