Knee Osteoarthritis and Thermal Spa Treatment

Evaluation of the Effectiveness of the Enghien-les-Bains Thermal Spa Treatment in the Rheumatology Indication in Patients With Knee Osteoarthritis. Indirect Comparison Study.

The goal of this interventional study is to evaluate the effectiveness at 6 months of the Enghien-les-Bains thermal spa treatment on functional disability and pain, assessed by the Minimal Clinically Important Improvement (MCII), in patients with knee osteoarthritis.

The study is conducted in patients aged 50 to 80 years with knee osteoarthritis (Kellgren-Lawrence grade 2 to 4) and a baseline functional impairment defined by a normalized WOMAC function score ≥ 30.

The main questions it aims to answer are:

• Does the Enghien-les-Bains thermal spa treatment result in a clinically meaningful improvement in pain and functional disability at 6 months in patients with knee osteoarthritis?
• Is the effectiveness of the Enghien-les-Bains thermal spa treatment superior to standard care, as assessed through an indirect comparison with an external control group from the ANGELLO randomized controlled trial (NCT0581943)? Patients receiving the Enghien-les-Bains thermal spa treatment are compared to the external control group of the ANGELLO randomized controlled trial (Saint-Jean-d'Angély), composed of non-spa-treated patients receiving standard care, to assess differences in pain and functional disability outcomes at 6 months.

Patients of the study:

• Undergo a standardized thermal spa treatment at Enghien-les-Bains.
• Continue usual medical care for knee osteoarthritis.
• Complete questionnaires and clinical assessments at baseline and at 6 months.

This study includes three medical visits with the investigator: one within 28 days before the thermal spa treatment, one at the end of the treatment, and one 6 months after the start of the treatment. At inclusion, informed consent is obtained, eligibility criteria are verified, and baseline data are collected, including self-administered questionnaires assessing pain, function, and quality of life before the start of the treatment.

During the 20-day thermal spa treatment, care provided and any adverse events are recorded. Clinical assessments and questionnaires are repeated at the end of the treatment. Additional patient-reported outcomes and treatment changes are collected at 3 months, and a final clinical evaluation and questionnaires are completed at 6 months.

An ancillary qualitative study evaluates the conditions under which the thermal spa treatment program is effective from the participants' perspective, including their engagement, lived experience, perceived benefits, facilitators and barriers, and any adaptations made. Data are collected through individual semi-structured face-to-face interviews at the end of the treatment, which are audio-recorded, fully transcribed, and qualitatively analyzed.

Inclusion Criteria:

• Knee osteoarthritis with Kellgren and Lawrence stage 2 to 4 evidenced by a knee X-ray examination in the past 3 years.
• 100-normalized score of the WOMAC physical function subscale greater than or equal to 30.
• Signed inform consent.
• With health insurance affiliation.

Exclusion Criteria:

• Presented with balneotherapy contraindication or to certain adjuvant treatment techniques (balneation, hydrotherapy jets, massage): chronic infectious pathology, active cancer, decompensated cardiac, hepatic or renal insufficiency, "open" leg ulcer, immune deficiency, phlebitis, erysipelas or history of erysipelas, active thrombosis, behavioral disorders, etc.
• Presented with chronic pain for reasons other than osteoarthritis: chronic inflammatory rheumatism (rheumatoid arthritis, ankylosing spondylitis, lupus, psoriatic arthritis) or fibromyalgia.
• Patient scheduled for knee osteoarthrosis-related surgery within the next 7 months.
• Having had spa treatment in the past 6 months whatever the indication or intra-articular corticosteroid injection within the previous 90 days or hyaluronic acid infiltration or other viscosupplementation or platelet-rich plasma (PRP) injection within the previous 6 months.
• Having planned a spa treatment in another indication between inclusion and final visit.
• Residing more than 30 kilometers from Enghien-les-Bains at the time of spa treatment.
• Women of childbearing potential who are not using effective contraception (estrogen/progestin or progestin-only oral, vaginal, transdermal, injectable or subcutaneous) or who plan to discontinue contraception within the next 7 months.
• Likely to be unable to comply with protocol or to attend visits, particularly in view of the duration of the research, or unable to read or understand French.
• Regulatory reason (guardianship or already enrolled in a clinical trial).
• Already included in a clinical trial or in the exclusion period of a clinical trial.