Feasibility and Preliminary Effects of Inspiratory Muscle Training in Patients With Knee Osteoarthritis Awaiting Total Knee Arthroplasty: An 8-Week, Pilot Randomized Controlled Trial.

Abstract

To evaluate the feasibility and preliminary effects of inspiratory muscle training (IMT) on aerobic capacity in patients with knee osteoarthritis (OA) awaiting total knee arthroplasty (TKA). Pilot randomized controlled trial. Laboratory, physical therapy center, and the physician's room. Forty participants with knee OA scheduled for TKA were randomized 1:1. Five withdrew before commencing the intervention, resulting in 35 participants (mean age ± SD, 66.8±7.2 years; 26 women) for the modified intention-to-treat analysis. The per-protocol analysis included 24 participants with ≥60% adherence. Both groups completed 8 weeks of home-based preoperative rehabilitation; the IMT group received additional IMT. The primary outcome was feasibility (recruitment, retention, adherence, safety). Secondary outcomes included aerobic capacity (maximum oxygen consumption [V̇o₂max]), estimated from the 6-minute walk test using a regression equation validated in older adults (SE=3.99 mL/kg/min). Additional outcomes included inspiratory muscle strength, pain intensity (numeric rating scale), knee function (Western Ontario and McMaster Osteoarthritis Index), and health-related quality of life (12-item Short Form Health Survey). The recruitment rate was 56%, and 31 participants completed baseline and postintervention assessments (retention 89%). Adherence rates were high (median IMT=100%; median control=92.5%), and no major adverse events occurred. In adherent participants (≥60%, n=24), IMT led to greater improvements in V̇o₂max than in controls (mean difference=2.38 mL/kg/min, 95% confidence interval, 0.77-3.98, P=.005). Inspiratory muscle strength increased significantly in the IMT group (absolute change=21.83 cmH₂O, relative change=0.31 cmH₂O/kg, all P<.001). Pain, knee function, and quality of life improved (all P<.05). An 8-week IMT program delivered alongside standard preoperative rehabilitation is feasible and safe and has the potential to improve estimated V̇o₂max and related outcomes in patients awaiting TKA. These pilot findings support the need for larger confirmatory trials.