Purpose: The objective of this study was to investigate the allele frequencies and genotype distributions of +45T/G (rs2241766) and +276 G/T (rs1501299) polymorphisms in AdipoQ gene, plasma adiponectin levels, and their associations in Thai knee osteoarthritis (OA) patients. Methods: Plasma samples were collected from 105 patients and 94 controls. Genomic DNA was isolated from peripheral blood of 202 patients and 196 controls. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect genotypes of +45T/G and +276G/T. The enzyme-linked immunosorbent assay (ELISA) was used to measure plasma adiponectin levels. Results: No statistically significant differences were identified between the two groups with respect to genotype distributions and allele frequencies of +45T/G and +276G/T (P>0.05). For +276G/T, significant differences were identified between Kellgren-Lawrence (KL) grade 2 and grade 3 (P=0.046), and between KL grade 2 and grade 4 (P=0.037) patients in the BMI <25 kg/m2 subgroup, a significant difference was found in the GG genotype of +45T/G (P+0.023). The mean plasma adiponection level of the OA group was lower than that of the control group (2.58+0.61 v.s. 2.78+0.68 ug/ml, P=0.033). Female plasma adiponection levels were higher than male levels in the control, OA and total group(p<0.05). Additionally , plasma adiponection levels of of female controls were statistically higher than females in the OA group (P<0.001). Plasma adiponection levels of the GG genotype were statistically higher than those of TT genotype at both the +45T/G and + 276 G/T loci, plasma adiponection levels of the control group were significantly higer than of the OA patient group (p=0.029, P+0.012 , respectively ). OA patients with th eGG genotype at the +276 G/T locus tended to have a higher than severity of OA when compared with GT and TT genotypes. Conclusion: The +45T/G and +276 G/T polymorphisms were not associated with the susceptibility of knee OA in a Thai population. However, GG genotypes of +45 t/G and + 276G/T polymorphism were associated with plasma adiponection levels in control and OA groups. High plasma adiponection levels may play a proctective role un the pathogenesis of knee OA, especially in Thai women.