The Effects of Walking Exercise Using Water Inertial Load on Dynamic Balance Ability and Pain in Women Aged 65 Years and Older with Knee Osteoarthritis: A Randomized Clinical Trial

<b>Background</b>: Aging reduces proprioception and neuromuscular control, leading to impaired balance and increased pain, particularly in women aged 65 years and older with knee osteoarthritis (KOA). Therefore, this study investigated the effects of walking exercise using a water inertial load on dynamic balance and pain in this population. <b>Methods</b>: Thirty-four women aged 65 years and older with KOA were recruited and randomly assigned to an experimental group (Aqua Vest group, <i>n</i> = 17) or a control group (weighted vest group, <i>n</i> = 17). After dropout, data from 28 participants were included in the analysis. Both groups performed the same walking exercise program twice weekly for eight weeks. Dynamic balance was evaluated using the Y-Balance Test (YBT), postural control using center of pressure (COP), and pain using the visual analogue scale (VAS). Data were analyzed using an analysis of covariance (ANCOVA) for between-group comparisons and the Wilcoxon signed-rank test for within-group changes. <b>Results</b>: The experimental group showed significantly greater improvement in YBT composite scores compared with the control group (<i>p</i> < 0.05). COP velocity showed a significant improvement in the anterior direction (<i>p</i> < 0.05), whereas no significant differences were observed in other directions. Pain decreased in both groups, but no significant between-group difference was observed. <b>Conclusions</b>: Eight weeks of walking exercise using a water inertial load significantly improved dynamic balance and showed a positive trend toward pain reduction in women aged 65 years and older with KOA. These findings suggest that the nonlinear inertial characteristics of water may enhance sensory-motor integration and postural control, contributing to improved balance performance.