Preliminary evaluation of a slipper-sock with lateral-wedge insoles on ground reaction forces, physical function, and pain in knee osteoarthritis

Abstract Medial knee osteoarthritis (KOA) is a leading cause of chronic disability. Conservative interventions like lateral wedge insoles offer symptom relief, but their biomechanical mechanisms remain unclear, especially during stair negotiation. This pre-post-trial evaluated a novel slipper-sock with lateral wedge insole (SOC) on GRF impulses, physical function, and pain in women with bilateral KOA. Fourteen females (mean age: 52.64 ± 6.98 years; BMI: 29.44 ± 2.98 kg/m²) with moderate bilateral medial KOA (Kellgren-Lawrence grades II–III; KOOS-confirmed) participated in this within-subjects trial. Participants completed level walking, stair ascent, and stair descent under barefoot and SOC conditions. Three-dimensional GRF impulses were calculated from force platform data (1000 Hz). Functional performance was assessed using Timed Up and Go (TUG), six-minute walk test (6MWT), and stair test (ST), with pain evaluated via visual analog scale (VAS). Statistical analyses employed paired t-tests and Wilcoxon signed-rank tests (α = 0.05). SOC significantly reduced vertical, anteroposterior, and mediolateral GRF impulses across all tasks ( p < 0.05). Exceptions included increased braking impulse during walking and stair descent, and increased maximum supination impulse during walking and stair descent. Clinically, SOC significantly improved TUG (13.75 ± 1.35 vs. 13.15 ± 0.76 s; p = 0.04) and 6MWT (374.07 ± 18.95 vs. 382.86 ± 21.96 m; p = 0.02), but did not affect ST ( p = 0.32) or VAS pain scores (all p > 0.05). The SOC attenuates most GRF impulses and enhances functional mobility, but does not improve stair-climbing or reduce pain. Design modifications are needed to mitigate increased braking and supination impulses. Future RCTs with larger, diverse samples should evaluate long-term outcomes, including fall risk.