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

This is a monocentric randomised non inferiority trial comparing 2 spa therapy protocols in symptomatic knee OA.

In the first group, 4 treatments (massages, showers, mud and pool sessions) are provided 6 days a week during 3 weeks. In the second group, the same 4 treatments are provided 3 days a week during 3 weeks then patients will follow an exercise program 3 days a week during 3 week.

Data will be collected at inclusion, 3 and 6 weeks and 3 and 6 months.

Inclusion criteria are:

• both gender
• uni or bilateral symptomatic knee OA
• pain VAS > 3 on a 0-10 scale)
• fulfilling ACR criteria for knee OA
• Kellgren and Lawrence stage 2 or over on standard radiograph

Non inclusion criteria are:

• severe comorbidity
• isolated femoro-patellar knee OA
• total knee replacement surgery expected during the next year
• other joint disease
• a contraindication or intolerance to any aspect of spa treatment (immune deficiency, evolving cardiovascular conditions, cancer, infection),
• spa treatment within the previous 12 months
• knee injection within the past month for corticosteroids and within the past 3 months for hyaluronic acids
• osteoarthritis (SYSADOA) change in the past 3 months
• massages, physiotherapy or acupuncture in the past month
• Patients will not be allowed to modify their non-steroidal antiinflammatory drug (NSAID) or their analgesic drug within the past 5 days and in the previous 12 h respectively.