Hydrotherapy for Osteoarthritis and Rheumatoid Arthritis: What Trials Found

Check First, and Keep Your Medicines

Water treatments for arthritis are, at most, an addition to care from your own clinician. Do not stop or change arthritis medicines because of anything below. Ask your doctor or physical therapist before starting water exercise or spa treatment if you have heart or blood pressure problems, are pregnant, or have reduced skin sensation. See hydrotherapy safety. This page gives no temperature, time or exercise plan; temperatures and doses appear only as what a study used.

Three Different Things Called Hydrotherapy

• Aquatic exercise means supervised or structured exercise in a pool, such as in water aerobics classes or aquatic physical therapy. Any benefit may come from the exercise itself rather than the water.
• Balneotherapy (spa therapy) means soaking in mineral or thermal water, sometimes with mud packs. For the terms, see hydrotherapy, balneotherapy and spa therapy compared.
• Home water practices include warm baths and hand or foot soaks.

These are studied differently, so they are separated below. Water studies cannot be blinded, which matters most for pain, a self-rated outcome.

Osteoarthritis: Aquatic Exercise

A Cochrane review of 13 trials (1,190 participants, mostly women with an average age of 68) found aquatic exercise caused a small short-term improvement compared with control in pain, disability and quality of life. [1] The average program lasted 12 weeks. No serious adverse events related to aquatic exercise were reported. [1] The reviewers rated 12 trials at low to unclear risk of bias for everything except blinding of participants and staff, which water-exercise trials generally cannot provide. [1]

A 2026 meta-analysis of 29 trials (1,984 participants) of aquatic rehabilitation in knee problems reported better symptoms and physical function than controls, with the largest benefit in knee osteoarthritis and in people under 60, and quality-of-life improvement that was not significant. [2]

Evidence label: established, modest, for knee osteoarthritis. Promising but limited for hip. Guidelines differ. The OARSI guideline lists structured land-based exercise as a core treatment and rates aquatic exercise as a lower-tier option for knee osteoarthritis, depending on other health conditions, and not recommended for hip or multi-joint osteoarthritis. [3] The American College of Rheumatology and Arthritis Foundation guideline gave strong recommendations for exercise in general. [4] NICE names therapeutic exercise as a core treatment. [5] Land exercise is the first-line comparison; see aquatic therapy and land-based exercise compared and aquatic therapy for osteoarthritis.

Osteoarthritis: Spa Bathing and Balneotherapy

A Cochrane review of seven trials (498 patients) found "silver level" evidence of benefit for mineral baths compared with no treatment, but called the evidence weak because of poor methods, and adverse events were not measured. [6] A 2023 systematic review of 17 trials reported that all showed improvement but noted many were of low quality. [7] The US National Center for Complementary and Integrative Health said in 2016 that high-quality research was too small for definite conclusions and that balneotherapy has a good safety record. [8] The ACR guideline listed "thermal modalities" among its conditional recommendations, without saying in its abstract which methods count, so it cannot be read as an endorsement of baths. [4]

Evidence label: promising but limited. An umbrella review of 49 reviews concluded spa therapy was beneficial for some musculoskeletal conditions, with improvements potentially lasting up to 9 months. [9] A 2025 meta-analysis of European balneotherapy trials in rheumatology (29 in mechanical disorders, 9 inflammatory, 4 fibromyalgia) rated the certainty of its pain and quality-of-life findings as very low. [10] Its authors reported receiving a grant from a French thermal research association. [10]

Rheumatoid Arthritis and Other Inflammatory Arthritis

• Aquatic exercise. A 2022 review found nine studies (604 participants) in inflammatory arthritis; two found aquatic exercise better than home exercise for pain. [11] The HydRA trial randomized women with rheumatoid arthritis to water or land aerobic exercise or no exercise; 100 were randomized and 82 completed, and the water group improved in disease activity and function. [12] A trial comparing two aquatic intensities found no significant difference between them on patient-reported outcomes in 89 people with mixed rheumatic diseases. [13] Promising but limited.
• Balneotherapy. The Cochrane review (nine studies, 579 participants) concluded the evidence is insufficient to show balneotherapy beats no treatment. [14] Insufficient evidence.
• Warm hand and foot baths. A small Turkish trial of 54 people compared six weeks of warm salt-water or plain warm-water baths with no bathing. Pain, fatigue and sleep scores improved in both bath groups compared with controls, though the group-by-time test was not significant for sleep or function. [15] The trial was registered retrospectively. [15] One small unblinded trial is insufficient evidence.

Fibromyalgia, Briefly

A 2024 meta-analysis of 16 trials of heated mineral water at 36 to 38 °C reported lower pain and disability that persisted up to 6 months. [16] The 2025 review above rated certainty very low overall. [10] Mixed.

The Bottom Line

A summary of systematic reviews found aquatic exercise had a small short-term effect on locomotor diseases, while the benefit of balneotherapy remained unclear. [17] No included trial in the Cochrane aquatic-exercise review assessed joint changes on X-ray, so effects on the disease itself are not known. [1] See Cochrane and guideline views.