1. Primary outcome measure: measuring the effect of spa treatment in patients suffering from lower limb osteoarthritis or any other lower limb rheumatological condition.

   Percentage of patients with minimum 19,9 mm decrease in pain Visual Analogue Scale (VAS) or WOMAC score (Western Ontario and McMaster Universities Arthritis Index) improvement of at least 9 points (minimal clinically important difference), 6 months after enrollment.

   Secondary outcome measures:

2. Measuring the effect of spa treatment in patients with concomitant chronic lower back pain.

   Percentage of patients presenting clinical benefits according to the EIFEL score, with a decrease of at least 5 points, 6 months after enrollment.

3. Quantitative evaluation of pain. Mean pain VAS comparison between enrollment and 6 months after spa treatment.

4. Quantitative evaluation of WOMAC score. Mean WOMAC score comparison between enrollment and 6 months after spa treatment.

5. Quantitative evaluation of EIFEL score. Mean EIFEL score comparison between enrollment and 6 months after spa treatment.

6. Impact of spa treatment on the patient's metabolism. Height and weight (BMI calculation), blood pressure and heart rate measured at enrollment and throughout the follow-up.

7. 8. Quality of life. 36-Item Short Form (SF 36) and EuroQol 5 Dimensions (EQ5D) questionnaires at enrollment, 3 months and 6 months.

9. Doctor and patient opinion. Semi-quantitative scale collected at enrollment, 3 months and 6 months.

10. Medicine consumption Daily medicine consumption evaluated upon the 72 hours preceding the medical visit at enrollment, 3 months and 6 months.

11. Auto-evaluation of pain VAS pain evaluation by the patient every 6 weeks for a more precise time frame of the treatment's effect.

Osteoarthritis and rheumatic conditions in general are a major public health issue, notably causing chronic pain disorders.

Spa treatments currently play a central role in the non-medical therapeutic arsenal for patients suffering from these rheumatic diseases.

A French study estimated the direct costs generated by osteoarthritis in France up to 1,6 billion euros in 2002, half of which was due to hospital expenses (800 million euros). Osteoarthritis required 13 millions consults and drug expenses of 570 million euros. Compared to 1993, these expenses increased by 156% due to the raise of the number of patients treated (+54%) and of the cost for each patient (+2,5% per year). This study concerned patients with lower limb osteoarthritis, and a significant portion of these expenses were attributable to the disease.

Chronic lower back pain is also a major health issue for its impact on patients' functional capacities as well as for the economic and social costs it generates. This is a frequent condition, it is estimated that 80% of the population will present lower back pain at some point in their life. Furthermore, epidemiological studies show an increase in the prevalence of lower back pain (3,9% in 1992 to 10,2% in 2006 in the American population).

Different well-conducted studies around the impact of spa treatments have led to the recognition of its beneficial outcome on the treatment of chronic lower back pain.

Several controlled, randomized, prospective trials have already evaluated the effect of spa treatment for other main indications claimed by crenotherapy in rheumatology such as hip and hand osteoarthritis, fibromyalgia, rheumatoid polyarthritis, psoriatic arthritis and chronic neck pain.

The THERMARTHROSE study by Forestier demonstrated the efficacy of spa treatments as a rheumatological indication for knee osteoarthritis using the WOMAC questionnaire and VAS pain scale. Following the model of this study, the investigators chose to use the WOMAC and VAS pain scale as the primary endpoints of the investigator's study.

The WOMAC questionnaire was developed by Bellamy in 1988, it is a functional index centered on the locomotor system.

The pain VAS is an auto-evaluation tool derived from visual analogue scales developed in psychiatry to measure patients' well-being. Today, this statistically measurable and reproductible tool is commonly used in clinical trials to monitor the evolution of pain and more precisely to evaluate the impact of a treatment on a given chronic disease such as osteoarthritis. For this study, pain will be measured using pain VAS according to Huskinsson and following methodology as recommended by French health authorities, with one measure.

During clinical studies in thermal environment, spa treatment is a composite entity including the effect of the water itself, but also physiotherapy, rest, education… The spa of Contrexéville wishes to obtain a new rheumatic indication. According to the recommendations of the Academy of Medicine, a prolonged observation of a cohort with repeated measures is required for any spa wishing to acquire the accreditation for a new orientation.

Towards this aim, the investigators wish to undertake a prospective study with repeated measures in order to analyze the evolution of the clinical state of patients with a rheumatic disease on the lower limbs or the rachis, 6 months after receiving a spa treatment in the Contrexéville thermal institute. Since rheumatological treatments at Contrexéville are not covered by health insurance, they will not be billed to the patients.

Inclusion Criteria:

• Patient presenting an indication for rheumatological spa treatment
• Patient with osteoarthritis or other rheumatic disease, located on the lower limbs with or without chronic lower back pain.
• Functional impairment with reduced mobility
• Life expectancy > 6 months
• VAS pain evaluation > 30 mm
• Available for a 6-months follow-up and an 18-days spa treatment
• Affiliation to the French social security system or equivalent
• Patient living within 100 kms of recruitment center

Exclusion Criteria:

• Patient having already underwent a spa treatment for rheumatic indication 6 months within enrollment
• Pregnancy, parturient or breast feeding
• Psychiatric illness or social situation that would preclude study compliance
• Predictable intolerance to thermal treatment (immunodeficiency, advanced cardiopathy, active cancer, active pulmonary tuberculosis, severe renal failure, cirrhosis, advanced dementia and severe mental conditions)