The influence of body mass index and velocity on knee biomechanics during walking.

Obesity has been associated with both the development and progression of knee osteoarthritis. Being overweight or obese from a young age is likely to decrease the age of onset for co-morbidities of obesity such as osteoarthritis. However, research on osteoarthritis has thus far focused on older adults. Therefore, the purpose of this study was to determine whether young adults who are overweight or obese exhibit biomechanical risk factors for knee osteoarthritis at either their preferred walking velocity or at 1m/s, which was slower than the preferred velocity. Thirty healthy young adults formed three equal groups according to body mass index. Three dimensional kinetics and kinematics were collected while participants walked overground at both velocities. Joint moments were normalized to fat free weight and height. The preferred walking velocity of obese participants was slower than that of normal weight individuals. There were no differences in knee flexion excursion, peak knee flexion angle, normalized peak knee flexion moment or normalized peak knee adduction moment among groups. Obese participants walked with lower peak knee adduction angle than both overweight and normal body mass index participants and several shifted towards knee abduction. All groups had smaller knee flexion excursion, peak knee flexion angle, peak knee flexion moment and peak knee adduction moment at 1m/s compared to preferred walking velocity. Overall, young and otherwise healthy overweight and obese participants have knee biomechanics during gait at preferred and slow walking velocities that are comparable to normal weight adults.