Objective　The objective of this study was to investigate the effect of a dietary supplement containing glucosamine hydrochloride, chondroitin sulfate and quercetin glycosides on knee joint functions in subjects with knee pain in stratified analysis based on Kellgren-Lawrence（K-L）grades.
Methods　A randomized, placebo-controlled, double blind intervention trial was conducted in 40 subjects with knee pain. They were randomly assigned to two groups and ingested either test supplement containing 1200 mg glucosamine hydrochloride, 60 mg chondroitin sulfate and 45 mg quercetin glycosides（GCQ supplement）per day or placebo for 16 weeks. Stratified analysis for the result about knee joint functions evaluated by Japanese Orthopaedic Association（JOA）criteria and visual analog scales（VAS）for knee pain was conducted in subject with K-L grades≦�T or K-L grades≧II.
Results　The result based on JOA criteria showed that change of the aggregate scores was significantly improved at week 8, 12, and 16 in the GCQ group compared to the placebo group in subject with K-L grades≦I, although that in subject with K-L grades≧II was not significantly improved. VAS for knee pain was not significantly improved in subject with K-L grades≦I or K-L grades≧II.
Conclusions　These results suggest that the daily supplementation of GCQ can be effective for improving knee joint functions in subjects with K-L grades≦I.