Objective： To evaluate the effects of 650 nm-10.6 μm combined laser in patients with knee Osteoarthritis （OA） and to determine whether the combined laser provides greater pain relief and improved function compared with red light. Methods： Forty-eight patients with knee OA were randomly allocated to two groups （24 per group）, receiving 20 min irradiation with 650 nm -10.6 μm combined laser or red light emitting diode respectively on point Dubi （ST 35） 3 times a week for the first course （2 weeks） and twice a week for the second one （4 weeks）. The main outcome measures were WOMAC （Western Ontario and McMaster Universities Osteoarthritis Index） scores. In addition, patients＇ global assessment, adverse effects and validation of patient blinding were analyzed. Results： All the patients completed the in：st course, but 12 were lost during the second one. Due to the high dropout rate by the second course, only the data acquired from the first course could be analyzed. No differences of general data of patients and WOMAC scores were found in between-group comparison before treatment （P〉0.05）. The WOMAC scores of patients in both combined laser group and red light group reduced significantly compared to baseline by the end of the first course （P〈0.01）. There were no significant differences on the reduction rate of WOMAC scores between two groups （P〉0.05）. Neither the patients＇ global assessment nor the dropout rate showed statistical differences between two groups （P〉0.05）. There was no difference between two groups in patients correctly guessing the treatment assignment （P〉0.05）. There was no significant difference in the reduction rate of WOMAC scores and the patients＇ global assessment between patients who guessed their assignment （P〉0.05）. Conclusion： Both combined laser and red light irradiation are beneficial to patients with knee OA. But as the statistical indifferences between two groups, the authors can＇t conclude from this study wheth
