FEASIBILITY OF ESTIMATING JOINT MOMENTS DURING GAIT WITH ONLY KINEMATIC DATA

A preliminary model is presented for estimating floor reaction forces during human walking based only on kinematic data. Such a model would be useful for supplementing purely qualitative gait analysis performed in clinics where force plates would be an unaffordable luxury, but not for situations in which quantitative data would be used in making such decisions as how to perform an orthopedic surgery. In this model, the vertical components of floor reaction forces are determined by conventional double differentiation of kinematic data, but the horizontal (fore-aft) components are based instead on constraints in which the floor reaction forces are characterized as acting through the center of mass of the upper body. To assess the accuracy of our calculations, we gathered data of gait by a healthy 22-year-old woman using a motion analysis system with force plates. Pathological gait data were also examined. Joint moments were computed from both force plate data and from our estimates of floor reaction forces. Prediction of vertical force showed higher reliability than prediction of fore-aft force. Joint moments from kinematics were successfully calculated in normal gait, but not in pathological gait, especially at the hip joint. The proposed approach may have some merit for performing a gait analysis even when no force plate is present, but the inaccuracy increases in the case of a subject whose upper body sways during gait.