Ninety patients with knee osteoarthritis were randomized to receive 12 sessions of high power laser therapy with either the addition of 2 months of oral glucosamine sulfate (n=45) or no additional treatment (n=45). The outcomes of interest were Visual Analog Scale (VAS) pain scores during activities of daily living, during the standardized stair climbing task, during the patellar grind evaluation (Rabot test), and during the Zohlen's sign or Rasping test. Outcomes were assessed upon completion of treatment, as well as at 6 months follow up. Results revealed no significant differences between the two groups in all outcomes at the end of treatment (p>0.05 for all), however at 6 months all VAS pain scores were significantly lower in the glucosamine group (p<0.05 for all).