A large randomized multicenter trial evaluated the effectiveness of spa therapy in the treatment of knee osteoarthritis. The study involved 187 control patients and 195 patients receiving spa therapy, all with knee osteoarthritis as defined by the American College of Rheumatology. The primary endpoint was the achievement of a minimal clinically important improvement (MCII) at 6 months, defined as a 19.9 mm reduction on the visual analogue scale (VAS) for pain or a 9.1 point improvement in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function score, without knee surgery. The spa therapy group showed a higher rate of achieving MCII (50.8%) compared to the control group (36.4%), with a statistically significant difference (χ²=8.05; p=0.005). However, no significant improvement in quality of life or patient acceptable symptom state was observed. The spa therapy group received 18 days of treatment, including massages, showers, mud applications, and pool sessions, in addition to home exercises and usual medical treatment. The control group received home exercises and usual treatment alone. The study found that spa therapy combined with home exercises and usual treatment provided a benefit over home exercises and usual treatment alone, and was well tolerated. The study aimed to fill the gap in evidence-based data regarding the efficacy of spa therapy for knee osteoarthritis. Despite previous small-scale studies, high-quality scientific evidence was lacking. The study's results suggest that a 3-week course of spa therapy, along with home exercises and usual medical treatment, offers benefit after 6 months compared to home exercises and usual treatment alone. The study was conducted in three major French spa resorts and followed patients for 9 months. Adverse events were minimal, with only one patient hospitalized for urinary lithiasis. The study's design used Zelen randomization to blind patients and reduce dropout rates. The results were internally consistent with the effect size found for the main endpoint. The study's findings support the use of spa therapy in the management of knee osteoarthritis, particularly when combined with home exercises and usual medical treatment. The results suggest that spa therapy may provide some benefit, although the exact mechanism is not fully understood. The study highlights the importance of patient compliance with home exercise programs and the potential role of spa therapy in enhancing this compliance. The study was registered with ClinicalTrials.gov (NCT00348777) and approved by the Ethics Committee of Lyon A.A large randomized multicenter trial evaluated the effectiveness of spa therapy in the treatment of knee osteoarthritis. The study involved 187 control patients and 195 patients receiving spa therapy, all with knee osteoarthritis as defined by the American College of Rheumatology. The primary endpoint was the achievement of a minimal clinically important improvement (MCII) at 6 months, defined as a 19.9 mm reduction on the visual analogue scale (VAS) for pain or a 9.1 point improvement in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function score, without knee surgery. The spa therapy group showed a higher rate of achieving MCII (50.8%) compared to the control group (36.4%), with a statistically significant difference (χ²=8.05; p=0.005). However, no significant improvement in quality of life or patient acceptable symptom state was observed. The spa therapy group received 18 days of treatment, including massages, showers, mud applications, and pool sessions, in addition to home exercises and usual medical treatment. The control group received home exercises and usual treatment alone. The study found that spa therapy combined with home exercises and usual treatment provided a benefit over home exercises and usual treatment alone, and was well tolerated. The study aimed to fill the gap in evidence-based data regarding the efficacy of spa therapy for knee osteoarthritis. Despite previous small-scale studies, high-quality scientific evidence was lacking. The study's results suggest that a 3-week course of spa therapy, along with home exercises and usual medical treatment, offers benefit after 6 months compared to home exercises and usual treatment alone. The study was conducted in three major French spa resorts and followed patients for 9 months. Adverse events were minimal, with only one patient hospitalized for urinary lithiasis. The study's design used Zelen randomization to blind patients and reduce dropout rates. The results were internally consistent with the effect size found for the main endpoint. The study's findings support the use of spa therapy in the management of knee osteoarthritis, particularly when combined with home exercises and usual medical treatment. The results suggest that spa therapy may provide some benefit, although the exact mechanism is not fully understood. The study highlights the importance of patient compliance with home exercise programs and the potential role of spa therapy in enhancing this compliance. The study was registered with ClinicalTrials.gov (NCT00348777) and approved by the Ethics Committee of Lyon A.