Primary Objective: To compare, after 12 weeks of double-blind treatment, the evolution of the improvement of pain (at rest and during / after exercise) in the questionnaire WOMAC (Western Ontario and McMaster Universities Arthritis Index), achieved with Condroflex ® oral administration(sulfate glucosamine + chondroitin sulfate sodium) in association with therapeutic exercises, compared to placebo in association with therapeutic exercises in individuals with knee OA and not exposed to prior treatment with the products under investigation.