Spa Therapy in Knee Osteoarthritis (OA): Nancy-thermal

Non-pharmacological treatments are recommended for the management of knee osteoarthritis (EULAR or OARSI recommendations) and some thermal modalities may be effective for relieving symptoms in knee Osteoarthritis. However supporting evidence is limited and nothing is known about the advantage of one modality of thermal therapy over another. The main objective of the study is to compare the number of patients achieving a composite response criteria associating the minimal clinically important improvement at 6 months, defined as ≥ 19.9 mm on the visual analogue pain scale and/or ≥ 9.1 points in a normalised Western Ontario and McMaster Universities osteoarthritis index function score and no knee surgery in 2 spa therapy protocols (a "usual protocol" and an "active protocol") in knee osteoarthritis. The secondary objectives are: 1. To compare the efficacy of the 2 protocols at 3 months. 2. To determine the evolution of quality of life and medical care consumption 3. To describe postural abnormalities 4. To determine predictive factors to a favourable response at 3 and 6 months