This study aimed to evaluate the effectiveness of spa therapy, combined with home exercises and usual medical treatment, in managing knee osteoarthritis compared to home exercises and usual treatment alone. A large multicentre randomized controlled trial was conducted in three major spa resorts in France from June 2006 to April 2007. Patients were randomly assigned to either the spa therapy group or the control group, with the primary endpoint being the number of patients achieving minimal clinically important improvement (MCII) at 6 months. The spa therapy group received 18 days of spa treatments, including massages, showers, mud applications, and pool sessions. The results showed that 50.8% of patients in the spa therapy group achieved MCII at 6 months, compared to 36.4% in the control group (p = 0.005). However, no significant improvement was observed in quality of life or patient acceptable symptom state at 6 months. The study concluded that an intensive course of spa therapy, combined with home exercises and usual treatment, provides medium-term benefits for patients with knee osteoarthritis, and is well tolerated.This study aimed to evaluate the effectiveness of spa therapy, combined with home exercises and usual medical treatment, in managing knee osteoarthritis compared to home exercises and usual treatment alone. A large multicentre randomized controlled trial was conducted in three major spa resorts in France from June 2006 to April 2007. Patients were randomly assigned to either the spa therapy group or the control group, with the primary endpoint being the number of patients achieving minimal clinically important improvement (MCII) at 6 months. The spa therapy group received 18 days of spa treatments, including massages, showers, mud applications, and pool sessions. The results showed that 50.8% of patients in the spa therapy group achieved MCII at 6 months, compared to 36.4% in the control group (p = 0.005). However, no significant improvement was observed in quality of life or patient acceptable symptom state at 6 months. The study concluded that an intensive course of spa therapy, combined with home exercises and usual treatment, provides medium-term benefits for patients with knee osteoarthritis, and is well tolerated.