Pool therapy after knee or hip replacement: what adding water buys you

The weeks after a knee or hip replacement are a balancing act: the new joint needs movement to regain range and strength, but the leg is swollen, weak and sore, and every land exercise loads it through gravity. Water changes the terms — buoyancy carries part of your body weight, warmth relaxes guarded muscle, and hydrostatic pressure works against swelling.

This systematic review asked whether adding aquatic therapy to standard land-based rehab actually improves outcomes after joint replacement. Across the three qualifying trials, the aquatic addition improved function, knee range of motion, and post-operative swelling compared with land-based rehab alone.

The evidence base is honestly thin: three small trials of moderate quality, and the authors themselves question whether the measured differences clear the bar of clinical significance. A 2026 meta-analysis of hydrotherapy after knee arthroplasty adds useful nuance — pain relief in water is comparable to land-based exercise rather than better, while muscle-strength gains modestly favour the pool.

The practical reading is the one we use in programming: water is not magic, it is a lower-load doorway. Early after surgery it lets clients move more, sooner and with less fear; as capacity builds, the program deliberately migrates to land, because full weight-bearing strength is the end goal. Extended health plans that cover kinesiology typically cover this progression.

Key findings

• Systematic review comparing aquatic-plus-land rehabilitation against land-based rehabilitation alone after hip or knee replacement.
• Function improved with the aquatic addition (standardised mean difference 0.53).
• Knee range of motion improved (SMD 0.78) and post-operative swelling fell (SMD −0.66).
• Only three small, moderate-quality trials qualified — the authors question whether the differences are clinically significant.
• A 2026 meta-analysis (Alrashedi et al.) adds: pain relief is comparable to land-based exercise, while muscle-strength gains favour hydrotherapy (g = 0.46).

Clinical relevance

Aquatic rehabilitation is one of our genuine differentiators, and joint-replacement recovery is its best use case: an earlier, gentler start that feeds into land-based strength work. This evidence supports exactly that sequence — water as the bridge, not the destination.

Prepared by the Volt Health team as an educational summary of the cited publication. It is not medical advice; assessment and treatment decisions should always be made with a qualified health professional.