ObjectiveTo systematically review the association between angiotension-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and osteoarthritis (OA) by using meta-analysis and trial sequential analysis (TSA). MethodsThe PubMed, EMbase, CNKI, CBM, VIP, and WanFang Data were searched up to October 12th, 2016 for case-control or cohort studies on the correlation between ACE I/D polymorphism and OA risk. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then, meta-analysis and TSA analysis were performed using Stata 13.1 software and TSA v0.9 soft ware. ResultsA total of six case-control studies involving 1 165 OA patients and 1 029 controls were included. The results of meta-analysis showed that the ACE I/D was associated with OA risk (DD+DI vs. II: OR=1.72, 95%CI 1.02 to 2.90, P=0.04; DI vs. II: OR=1.65, 95%CI 1.06 to 2.56, P=0.03). Subgroup analysis of ethnicity showed that, in Caucasians, the ACE I/D was associated with OA risk (DD vs. DI+II: OR=2.10, 95%CI 1.54 to 2.85, P<0.01; DD+DI vs. II: OR=3.11, 95%CI 2.20 to 4.39, P<0.01; DD vs. II: OR=4.01, 95%CI 2.68 to 6.00, P<0.01; DI vs. II: OR=2.65, 95%CI 1.06 to 2.56, P<0.01; D vs. I: OR=2.11, 95%CI 1.72 to 2.58, P=0.73). And TSA showed that all of the cumulative Z-curve strode the conventional and TSA threshold value which suggested the result of the association between ACE I/D polymorphism and OA in Caucasians was very reliable. However, the association did not exist in Asians (DD vs. DI+II: OR=0.80, 95%CI 0.60 to 1.07, P=0.13; DD+DI vs. II: OR=1.08, 95%CI 0.87 to 1.35, P=0.49; DD vs. II: OR=0.86, 95%CI 0.62 to 1.20, P=0.38; DI vs. II: OR=1.18, 95%CI 0.93 to 1.50, P=0.19; D vs. I: OR=0.93, 95%CI 0.83 to 1.14, P=0.73). And the results of TSA displayed that all of the cumulative Z-curve did not strode both TSA threshold value and required information size line excepting for DD vs. DI+II genetic model which suggested that the sample-size in Asians was insufficient. ConclusionsThe ACE D allele maybe a risk factor for OA in Caucasians. However, the association between ACE I/D polymorphism and OA risk in Asians still need more studies to prove.