Aquatic Exercise Prescription for Patients with Knee Osteoarthritis: Designing Buoyancy-Assisted Weight Reduction and Water Resistance Training

Introduction

The prevalence of knee osteoarthritis (OA) in Taiwan reaches 40–50% among those aged 65 and above, making it the leading cause of mobility impairment in middle-aged and older adults. Traditional land-based exercise often deters many patients due to joint weight-bearing concerns, whereas aquatic exercise leverages the principle of buoyancy to complete strength training and aerobic exercise in an environment with nearly zero joint impact. It is listed by the Taiwan Society of Rehabilitation Medicine as one of the first-line non-surgical treatment recommendations for osteoarthritis.

Biomechanical Principles of Buoyancy-Assisted Weight Reduction

The degree to which buoyancy reduces joint load is directly related to water depth:

For patients with knee osteoarthritis, exercising in waist-to-chest-deep water reduces joint loading to only 25–50% of that on land, significantly decreasing pain and enabling patients to perform movements that are impossible on land.

Strength Training Mechanisms in Aquatic Exercise

Although buoyancy reduces joint load, the hydrodynamic drag of water provides resistance from all directions, resulting in:

• Quadriceps (knee extension) and hamstrings (flexion) are both trained during aquatic exercise
• Water resistance increases with the square of movement speed, so faster movements produce greater training effects, and patients can self-regulate speed to control intensity
• Balance challenges in water activate deep stabilizer muscles, improving knee proprioception

Aquatic Exercise Prescription for Knee Osteoarthritis

Foundation Phase (Weeks 1–4): Aimed at pain relief and restoring range of motion

• Water walking: forward, backward, and lateral movements, 5 minutes per direction
• Wall-supported leg raises: standing knee lifts and side leg raises, 10–15 reps per side × 2 sets
• Water cycling: alternating pedaling motion with both feet, sustained for 5–10 minutes
• Water ankle pumps: seated at pool edge, flexing and extending the ankles to promote blood circulation

Strengthening Phase (Weeks 5–12): Aimed at increasing quadriceps strength and improving function

• Water squats: hands on pool wall, squatting to a 60–90° knee angle, 10–15 reps × 3 sets
• Water lunges: in chest-deep water, stepping forward with one leg, 5–10 reps × 2 sets
• Use aquatic resistance bands or aquatic dumbbells to increase resistance
• Swimming (breaststroke or freestyle kicking): kicking movements strengthen the quadriceps, 15–20 minutes per session

Maintenance Phase (after Week 12):

• Aquatic exercise 3–4 times per week
• Gradually introduce some land-based exercise (such as brisk walking), based on post-strengthening joint conditions

Relevant Medical Resources in Taiwan

• NHI-reimbursed aquatic physical therapy: Some medical centers (e.g., National Taiwan University Hospital, National Cheng Kung University Hospital, Hualien Tzu Chi Hospital) have rehabilitation departments with aquatic therapy pools; NHI coverage is available after physician referral
• Self-pay aquatic classes for osteoarthritis: Rehabilitation clinics or hydrotherapy centers across Taiwan offer self-pay programs, costing approximately NT$600–1,200 per session
• Taiwan Orthopaedic Association educational resources: Provides exercise guidelines for osteoarthritis, downloadable from their official website

Practical Recommendations

1. Take physician-prescribed pain medication (such as NSAIDs) 30 minutes before swimming to help complete exercise in a pain-free state; pushing through pain is not advised.
2. Choose a warm-water pool at 32–34°C; the thermal effect aids joint warm-up and muscle relaxation.
3. Use an entry platform with handrails when entering and exiting the water to avoid undue torsional stress on the knee joints.
4. Avoid squats beyond 90° or rapid directional changes, as these movements place greater stress on degenerated menisci.
5. If joint swelling or increased pain persists for more than 2 hours after exercise, return for a follow-up to assess whether exercise intensity should be adjusted.

Conclusion

Aquatic exercise is the optimal bridge for patients with knee osteoarthritis to achieve “pain-free mobility.” The decompressive protection provided by buoyancy combined with the training benefits created by water resistance allows patients to effectively strengthen the muscles around the knee in a safe environment, slowing the progression of joint degeneration. Taiwan’s increasingly comprehensive aquatic physical therapy resources enable more patients to enjoy this therapeutic exercise that balances scientific rigor with comfort.

Related Reading

• Joint Protection Through Water Training: Aquatic Rehabilitation Programs for Osteoarthritis
• Swimming for Joint Protection: Swimming Recommendations for Osteoarthritis Patients
• Swimming and Joint Protection: The Best Choice for Low-Impact Exercise
• The Therapeutic Effects of Swimming on Arthritis: Rehabilitation Applications of Aquatic Resistance Training