Intrasubject Gait Variability During Stair Walking in Knee Osteoarthritis: A Kinematic and Kinetic Analysis.

Background: Gait variability in kinematic and kinetic parameters during stair walking is a key indicator of motor function and fall risk in individuals with knee osteoarthritis (KOA). However, normative reference data and pathological patterns in KOA remain under explored. Methods: This cross-sectional study analyzed retrospective data from 169 participants, including 116 individuals with KOA and 53 matched healthy controls. Each participant performed both stair ascent and descent tasks, during which lower limb kinematic and kinetic gait parameters were obtained using a three-dimensional motion capture (3DMC) system and an instrumented staircase. Intrasubject variability, quantified by coefficient of variation (CV), was calculated for all gait parameters. A mixed between-within subject analysis of variance with aligned rank transformed data was conducted to assess the effects of group (KOA vs. control), condition (stair ascent vs. descent), and their interaction. Results: Individuals with KOA exhibited significantly greater kinematic variability during both stair ascent and descent, whereas greater kinetic variability was observed only in knee and hip joint moments and powers during ascent. Across both groups, variability increased at the knee and distal segments, but decreased at proximal segments (hip and pelvis) during stair ascent compared with descent. KOA individuals displayed distinct adaptation mechanism between stair ascent and descent, but not in kinematic parameters. Conclusion: Individuals with KOA demonstrate significantly increased movement variability compared with healthy controls during stair walking, especially in knee and hip joint moments and powers during ascent. These findings indicates distinct and task-specific adaptation strategies in KOA, reflecting altered stability and joint loading mechanisms.