Medically reviewed | Last updated: August 2026
If you have knee pain and someone told you to go swimming, your first reaction might be scepticism. But the research on aquatic exercise for knee osteoarthritis is genuinely compelling. Water removes almost all of your body weight from your joints while still allowing your muscles to work hard — exercise that builds strength and improves range of motion with a fraction of the joint stress of land-based exercise.
Why Water Is Ideal for Arthritic Knees
Buoyancy is the key mechanism. When submerged to your waist in water, you experience roughly 50% less body weight on your joints. Submerged to your chest, it drops to around 25%. Water also provides resistance in all directions, engaging more muscles and improving multi-directional joint stability. Warm water (33–35°C) additionally reduces muscle spasm, improves circulation, and decreases pain perception.
A 2016 Cochrane review update found aquatic exercise produced small but clinically relevant reductions in pain and improvements in function and quality of life for people with knee and hip osteoarthritis. A 2019 network meta-analysis in BMJ Open found aquatic exercise among the most effective non-pharmacological interventions for knee OA pain. According to the Arthritis Foundation’s guide to water exercise, aquatic therapy is recommended for arthritis patients who cannot tolerate land-based exercise.
Swimming Exercises for Knee Osteoarthritis
1. Water Walking
Stand in chest-depth water and walk forward normally for two lengths of the pool, then backward. Walking backward activates the quadriceps in a way that reduces anterior knee stress. Start with 10 minutes and build to 30 over four weeks.
2. Water Leg Raises
Stand at the pool edge holding the rail. Keeping your knee straight, lift your right leg forward to approximately 45 degrees, hold for two seconds, then lower slowly. Repeat to the side, then behind. Do 10–15 repetitions on each side. Research shows every kilogram of quadriceps strength reduces knee joint load by approximately four kilograms during walking.
3. Water Squats
Stand in shoulder-depth water with feet hip-width apart. Slowly lower into a squat, going only as deep as comfortable (typically 30–45 degrees initially). The buoyancy supports your weight as you lower and creates resistance as you rise. Do 10–15 repetitions.
4. Flutter Kicks (Pool Noodle Float)
Hold a pool noodle under your arms and float face-down. Perform gentle, continuous flutter kicks — small, rapid alternating leg movements driven from the hip. Start with 30 seconds and build to 2–3 minutes. Flutter kicks gently mobilise the knee through its full range of motion, pumping synovial fluid through the joint.
5. Side Stepping
In waist-to-chest-depth water, step sideways continuously for the length of the pool, then return the other way. Side stepping specifically targets the hip abductors and glute medius — muscles that stabilise the knee and pelvis during gait. Weakness in these muscles is strongly associated with progression of knee OA.
6. Stair Stepping (Pool Step)
Use pool steps for step-ups: step up with your right foot, bring the left up, step down with the right, bring the left down. Repeat for 2 minutes leading with each leg. This builds functional strength for stairs with dramatically reduced joint loading.
7. Bicycle Kicks (Floating)
Hold the pool edge behind you, float with your body horizontal, and perform a cycling motion — alternating pushing each knee forward and drawing it back in a smooth, circular pattern. Aim for 2–3 minutes continuously. Use a pool noodle under your hips for support if needed.
How Often Should You Do Aquatic Exercise?
Research suggests three sessions per week produces the best outcomes for knee OA. Each session should last 30–45 minutes when you have built up your tolerance. Start with two sessions per week of 15–20 minutes if you are new to aquatic exercise. Monitor your pain response in the 24 hours after exercise — significant increase in joint pain or swelling indicates you have done too much.
What to Watch Out For
Cold water can increase muscle spasm and pain in arthritic joints — warm water pools are significantly more beneficial. Avoid breaststroke if you have knee OA — the frog-kick motion puts significant rotational stress on the medial compartment. Freestyle (front crawl) with flutter kicks is a much better choice.
The Bottom Line
Swimming and aquatic exercise are among the best-evidenced, lowest-risk interventions for knee osteoarthritis. Start gently, build progressively, and be consistent. Three sessions per week for eight weeks is enough to see measurable improvements in pain, strength, and function.
Frequently Asked Questions
Is swimming good for knee osteoarthritis?
Yes — swimming and aquatic exercise are among the most evidence-backed interventions for knee osteoarthritis. Water reduces joint load by 25–50% depending on depth of submersion, allowing meaningful exercise without the compressive stress that worsens pain on land. A 2016 Cochrane review update confirms small but clinically relevant pain reduction and functional improvement from regular aquatic exercise in people with knee OA.
Which swimming stroke is best for arthritic knees?
Freestyle (front crawl) with flutter kicks is the best stroke for knee osteoarthritis — the kick is gentle and linear, avoiding rotational stress on the knee. Backstroke is also suitable. Avoid breaststroke entirely — the frog-kick motion puts significant rotational and medial compartment stress on the knee that frequently aggravates OA symptoms.
How long should I swim for knee pain?
Start with 15–20 minutes per session if you are new to aquatic exercise or in significant pain. Build to 30–45 minutes over 4–6 weeks. Research studies showing significant improvement in knee OA symptoms typically use 30–45 minute sessions, three times per week, for 8–12 weeks. The most important factor is consistency — three moderate sessions per week outperforms two intense sessions.
Can I do water exercises for knee pain if I can’t swim?
Absolutely — you don’t need to swim to benefit from aquatic exercise for knee OA. Water walking, water leg raises, side stepping, and wall squats in the shallow end are all highly effective and require no swimming ability. These exercises can be done standing in chest-depth water holding the pool rail for stability. Many physiotherapy-led hydrotherapy programmes are entirely non-swimming based.
Does warm water help knee osteoarthritis?
Yes — warm water (33–35°C) provides additional benefits beyond buoyancy for knee OA. Heat reduces muscle spasm, improves circulation to the joint, decreases pain perception, and makes movement easier and more comfortable from the start of your session. Cold pools are significantly less therapeutic and can increase muscle guarding. If your regular pool is cold, a wetsuit can help, or seek out a hydrotherapy pool kept at therapeutic temperatures.
How many times a week should I do aquatic exercise for knee OA?
Research consistently shows three sessions per week produces the optimal balance of stimulus for adaptation and recovery time for people with knee osteoarthritis. Two sessions per week produce meaningful but smaller benefits. Daily aquatic exercise is generally safe given the low joint loading, but most people with OA find three sessions per week is the sweet spot for sustained improvement without fatigue.
Will aquatic exercise slow the progression of knee osteoarthritis?
Strong evidence supports that regular exercise — including aquatic exercise — slows knee OA progression by maintaining the strength and muscle mass around the joint that reduces loading on the cartilage. The anti-inflammatory effect of regular moderate exercise also reduces synovitis. While no exercise can regenerate lost cartilage under current standard-of-care treatment, consistent aquatic exercise is one of the most effective disease-modifying lifestyle interventions available.
Trusted External Resources
- Arthritis Foundation — Benefits of Water Exercise
- Mayo Clinic — Osteoarthritis: Diagnosis and Treatment
- Knee Osteoarthritis: Symptoms, Causes and Treatment (our pillar guide)
References
- Bartels EM, et al. “Aquatic exercise for the treatment of knee and hip osteoarthritis.” Cochrane Database of Systematic Reviews, 2016. https://pubmed.ncbi.nlm.nih.gov/27007113/
- Fransen M, et al. “Exercise for osteoarthritis of the knee: a Cochrane systematic review.” British Journal of Sports Medicine, 2015. https://pubmed.ncbi.nlm.nih.gov/25452250/
- Arthritis Foundation. “Benefits of Water Exercise.” https://www.arthritis.org/
- Mayo Clinic. “Osteoarthritis.” https://www.mayoclinic.org/
This article is for informational purposes only. Always consult your doctor or physiotherapist before starting a new exercise programme, especially if your osteoarthritis is severe.
