Aquatic Therapy for Knee Osteoarthritis

Knee osteoarthritis is one of the most common musculoskeletal disorders worldwide and a leading cause of pain, reduced mobility and loss of physical function. A 2026 meta-analysis demonstrates that aquatic therapy for knee osteoarthritis provides significant clinical benefits compared with comparable land-based physiotherapy programmes.

By analysing nine randomized controlled trials involving 423 participants, researchers found that aquatic therapy significantly reduces pain and joint stiffness while offering additional improvements in joint mobility and physical function.

Why aquatic therapy benefits people with knee osteoarthritis

People living with knee osteoarthritis often experience chronic pain, joint stiffness and difficulty performing everyday activities. These symptoms frequently limit participation in traditional exercise programmes.

Aquatic therapy provides a supportive rehabilitation environment where buoyancy reduces joint loading while water resistance allows patients to strengthen muscles without excessive stress on the knee joint.

The combination of warm water, hydrostatic pressure and natural resistance enables patients to exercise comfortably while improving joint function.

Key findings of the meta-analysis

The researchers compared aquatic therapy with land-based physiotherapy across nine randomized controlled trials.

The results demonstrated several important clinical benefits.

Significant pain reduction

Aquatic therapy produced significantly greater reductions in knee pain compared with land-based exercise.

The pooled analysis showed a moderate but clinically meaningful reduction in pain, making movement and daily activities more comfortable for patients.

Reduced joint stiffness

Patients participating in aquatic therapy experienced significantly less joint stiffness than those following land-based rehabilitation programmes.

Improved joint flexibility can help patients perform walking, stair climbing and other daily activities more comfortably.

Improved range of motion

The analysis found improvements in knee joint range of motion following aquatic therapy.

Although these improvements were not statistically significant compared with land-based physiotherapy, the overall trend favoured water-based rehabilitation.

Better physical function

Aquatic therapy also improved physical function and mobility.

While the difference compared with land-based rehabilitation did not reach statistical significance, patients generally demonstrated better functional performance after completing aquatic exercise programmes.

Why water-based exercise is effective for knee osteoarthritis

The therapeutic properties of water create an ideal environment for people with painful knee joints.

Buoyancy reduces joint loading

Water supports a large proportion of body weight, substantially reducing compressive forces acting on the knee joint.

This allows patients to perform movements that might otherwise be painful on land.

Warm water decreases pain and muscle tension

Most rehabilitation programmes included water temperatures between 32°C and 34°C.

Warm water promotes muscle relaxation, improves circulation and helps decrease pain perception while increasing connective tissue flexibility.

Hydrostatic pressure supports the joints

Hydrostatic pressure provides gentle compression around the lower limbs, helping reduce swelling while improving proprioception and joint stability.

Water resistance strengthens muscles safely

Water offers natural resistance throughout every movement.

This enables patients to strengthen the muscles surrounding the knee without exposing the joint to high impact forces that commonly occur during land-based exercise.

Typical aquatic therapy programme

Across the included studies, aquatic therapy programmes generally consisted of:

• Water temperature between 32°C and 34°C
• 2–5 sessions per week
• 20–60 minutes per session
• Programme duration between 3 and 16 weeks
• Exercises focusing on strengthening, walking in water and improving joint mobility

The authors note that exercise dosage varied considerably between studies, making it difficult to determine the optimal treatment protocol.

Clinical implications

This meta-analysis provides strong evidence that aquatic therapy for knee osteoarthritis is an effective non-pharmacological treatment option.

Aquatic therapy may be particularly valuable for patients who experience:

• Pain during weight-bearing activities
• Joint stiffness
• Reduced walking ability
• Limited tolerance for land-based exercise
• Reduced confidence during movement

For these patients, hydrotherapy offers a comfortable and low-impact environment that supports rehabilitation while reducing stress on the affected joints.

Outcome measures used in the review

The included studies evaluated treatment effectiveness using internationally recognised clinical outcome measures, including:

• Visual Analogue Scale (VAS)
• WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index)
• Range of Motion (ROM)
• SF-12 and SF-36 Quality of Life questionnaires
• International Society of Osteoarthritis Management (ISOM) measures

These assessments measured pain, stiffness, mobility, physical function and quality of life throughout the rehabilitation programmes.

Conclusion

This 2026 meta-analysis confirms that aquatic therapy for knee osteoarthritis significantly reduces pain and joint stiffness compared with land-based physiotherapy.

The review also found positive trends towards improved range of motion and physical function, making aquatic therapy a valuable non-pharmacological intervention for managing knee osteoarthritis.

The authors conclude that aquatic therapy should be considered an effective component of comprehensive rehabilitation programmes for people with knee osteoarthritis.