Background: Approximately 33% of the adult population in the United States is considered obese (28), which increases the risk of comorbidities such as osteoarthritis (OA) (34). The most notable feature of OA is the loss of articular cartilage within a joint, resulting in pain and physical disability (3). The association between obesity and OA is due to a combination of mechanical and metabolic factors (3). Greater weight from obesity adds stress to articular cartilage in weight-bearing joints, and contributes to cartilage breakdown (21). Previous studies have demonstrated an association between gait biomechanics and OA in older populations (15, 25), but data are lacking in young obese individuals without OA. Young obese compared to normal weight adults have lesser knee flexion excursion (KFE) (31), and greater vertical loading rates (vLR) during gait (30, 31). However, the source of aberrant gait mechanics in obese adults is unclear, and could be related to impaired shock attenuation from weakened musculature in the lower extremity. Obese young adults have deficits in quadriceps function after normalizing to fat-free mass, and walk slower compared to normal weight young adults. RTD was moderately associated with KEM at habitual gait speed, and KEM was also lesser in obese compared to normal weight adults. The lesser KEM in the obese group suggests that obese young adults walk with a quadriceps avoidance gait, which may contribute to knee OA development. Exercise interventions targeting RTD may be useful for improving walking mechanics in obese adults.
Listed In: Biomechanics, Gait, Orthopedic Research

Effects of Wide Step Width on Stair Ascent Knee Kinetics in Obese Participants

Purpose: An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moments. Increases in step width may act to reduce this moment. The purpose of this study was to determine the effects of increased step width on knee biomechanics during stair ascent of healthy-weight and obese participants. Methods: Participants ascended stairs while walking at their preferred speed in two different step width conditions – preferred and wide. A 2 x 2 (group x condition) mixed model analysis of variance (ANOVA) was performed to analyze differences between groups and conditions (p<0.05). Results: Increased step width decreased the loading-response peak vertical ground reaction force (GRF), loading-response knee abduction moment, knee extension ROM, and knee abduction ROM in both groups. However, it also increased loading and push-off peak mediolateral GRF, and peak knee abduction angle in both groups. Obese participants experienced a disproportionate increase in loading and push-off peak mediolateral GRF, and peak knee abduction angle compared to healthy. Conclusion: Increased SW successfully decreased loading-response peak knee abduction moment. Implications of this finding are that increased SW may decrease likelihood of developing medial compartment knee osteoarthritis. This study shows that this gait modification affects obese and healthy-weight differently, and the influence of body mass on knee biomechanics.

Listed In: Biomechanics