The effect of a frontal plane gait perturbation bout on knee biomechanics and muscle activation in older adults and individuals with knee osteoarthritis

Background: Walking can be a challenging task for individuals with knee osteoarthritis and many older adults. The purpose was to determine the immediate effect of a frontal plane perturbation bout during walking on knee biomechanics and muscle activation patterns in these groups. Methods: 44 asymptomatic older adults and 32 individuals with knee osteoarthritis were recruited. Sagittal and frontal plane knee biomechanics and muscle activation levels were calculated and recorded during treadmill walking. After a baseline collection at 6-min, a random series of unexpected medial/lateral walkway surface perturbations were delivered over approximately 24 min. Data was collected immediately after the perturbations. Discrete measures extracted from biomechanical waveforms, and principal component analysis to analyze muscle activation were utilized to determine time effects and interactions using analysis of variance models (alpha = 0.05). Findings: After the perturbation bout, sagittal plane range of motion was significantly increased in the osteoarthritis group (Effect Size = 0.24) and in both groups peak knee adduction moment (Effect Size = 0.10) and difference between peak flexion and extension moments (Effect Size = 0.16) were significantly increased. Muscle amplitudes in both groups were significantly reduced (PP1-scores) after perturbation bout, whereas significant time-based gait cycle activation pattern alterations identified by PP2-and PP3-scores were related to group and muscle assignment. Interpretation: Perturbations were tolerated by all participants, resulting in significant alterations to biomechanical outcomes and muscle activation levels and patterns. Demand on the knee joint was not increased after perturbations. Gait perturbation training in these groups may be feasible using a frontal plane perturbation bout.