Effects of Six-Week Off-axis Stepping Training on Individuals with Medial Knee Osteoarthritis

Abstract\u2014 This study investigates whether a subject-specific off-axis stepping training program can reduce peak knee adduction moment (pKAM) and improve frontal plane stability and clinical outcomes in individuals with medial knee osteoarthritis (KOA). Twelve participants with medial KOA completed 18 training sessions over six weeks using a custom off-axis robotic elliptical stepping system designed to reduce pKAM and improve frontal-plane movement control. Outcome Measures: Peak knee flexion moment (pKFM), pKAM, peak knee internal rotation moment (pKIRM) during stepping; Knee Injury and Osteoarthritis Outcome Score (KOOS); Timed Up and Go (TUG); 20-meter walk test (20MWT); 30-second sit-to-stand (STS); Four Square Step Test (FSST); spatiotemporal gait parameters; maximum lateral and medial footplate sliding distance; and frontal plane sliding instability. Pre- and post-training outcomes (and 6-week follow-up) were compared with paired t-tests (Bonferroni corrected \u03b1 = 0.05). Results: Training reduced pKAM significantly by 29 % (p = 0.010). KOOS Symptoms improved by 18% (p=0.036), 20MWT time improved by 12% (p = 0.024), gait velocity increased by 6% (p = 0.018), and step length increased by 4% (p=0.046). Stepping speed increased by 51% (p=0.026), sliding instability (mediolateral variability) decreased by 66% (p<0.002), and maximum lateral sliding distance increased by 8% (p=0.022). Improvements in sliding instability (p=0.038) and lateral sliding distance (p=0.040) remained significant at 6-week follow-up. Conclusion: A six-week subject-specific off-axis stepping training program effectively reduced knee joint loading (pKAM) and frontal-plane instability, and improved symptoms and functional performance in individuals with medial KOA.