 This phase III clinical study will be conducted in Brazilian research sites. It will be included in the study 314 participants diagnosed with primary knee OA according to the classification criteria of the ACR. After a washout period, the participants will be randomized to receive the combination of glucosamine sulfate chondroitin sulfate of bovine origin of Eurofarma Laboratorios S.A. N 157 or the combination of glucosamine sulfate chondroitin sulfate of Zodiac Pharmaceuticals S.A. Condroflex N 157. The treatment period of the study will be of 24 weeks. Each participant will perform seven visits to the research site. The main evaluations will be the improve of pain in the target knee by questionnaire Western Ontario and McMaster Universities Osteoarthritis Index WOMAC and quality of life by SF-12 questionnaire. 