Effects of Wider Step Width on Knee Biomechanics in Obese and Healthy-Weight Participants During Stair Ascent

An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moment. Increases in step width may act to reduce this moment. This study focused on how step width influenced the knee joint during stair ascent by healthy and obese participants. Participants ascended stairs while walking at their preferred speed and under one of two step width conditions – preferred and increased. Obese participants experienced greater mediolateral and vertical ground reaction forces (GRFs), as well as increased peak knee extensor moments and push-off peak internal knee adduction moments. The findings of this study indicate that when step width increases, obese participants will experience a disproportionate increase in Loading-response and push-off response peak mediolateral GRF, push-off peak knee adduction moments, and peak knee adduction angle compared to healthy participants. When normalized to lean body mass, obese participants also had greater increases in peak knee extension moments under the increased step width condition. Participants in each group experienced decreased in loading-response peak vertical GRF, loading-response peak knee abduction moment, peak knee internal rotation moment, knee extension range of motion, and knee abduction range of motion, and increased loading-response and push-off response peak mediolateral GRF, push-off peak knee adduction moment, peak knee external rotation moment, peak knee abduction angle, and knee internal rotation range of motion. This study provides important information regarding differences in knee joint biomechanics during stair ascent between obese and healthy populations.