Despite the widespread provision of aquatic physical therapy for people with hip or knee OA, there is little evidence attesting to its efficacy in this population. Although many studies have reported positive effects of hydrotherapy interventions in cohorts with various arthritic conditions,10 few have evaluated a sample selected on the basis of knee or hip OA alone. A
recent study found no significant benefit of hydrotherapy over a gym-based program or no intervention for symptoms in people with hip or knee OA authors made use of nonfunctional
body positions and had a limited capacity for progression, features that
may explain their nonsignificant findings. Methodological limitations in other published studies on OA include inadequate sample size, nonrandom allocation, and no intention-to-treat
analysis.Furthermore, most hydrotherapy programs demonstrate little consideration of hydrostatic or hydrodynamic principles in their choice of exercises, thus reducing the potential
for benefit from the overall program.The present study was designed to address the limitations of previous studies through the use of an adequately powered randomized controlled trial
with intention-to-treat analysis and a functional progressive intervention that maximized the unique properties of water to optimize outcomes.