Measurement of lower extremity kinematics during level walking

Abstract

Summary: A simple external marker system and algorithms for computing lower extremity joint angle motion during level walking were developed and implemented on a computer-aided video motion analysis system (VICON). The concept of embedded axes and Euler rotation angles was used to define the three-dimensional joint angle motion based on a set of body surface markers. Gait analysis was peformed on 40 normal young adults three times on three different test days at least 1 week apart using the marker system. Angular motion of the hip, knee, and ankle joints and of the pelvis were obtained throughout a gait cycle utilizing the three-dimensional trajectories of markers. The effect of uncertainties in defining the embedded axis on joint angles was demonstrated using sensitivity analysis. The errors in the estimation of joint angle motion were quantified with respect to the degree of error in the construction of embedded axes. The limitations of the model and the marker system in evaluating pathologic gait are discussed. The relatively small number of body surface markers used in the system render it easy to implement for use in routine clinical gait evaluations. Additionally, data presented in this paper should be a useful reference for describing and comparing pathologic gait patterns. Key Words: Gait analysis-Joint angles-Gait parametersBiomechanical model-Sensitivity analysis.Quantitative gait analysis is an important clinical tool for quantifying normal and pathological patterns of locomotion, and has been shown to be useful for prescription of treatment as well as in the evaluation of the results of such treatment (1,6,16,17). Typically, data acquired during a clinical gait analysis include relative positions and orientations of body segments, foot-floor reaction forces, temporal-distance parameters, and phasic activity of muscles of the lower extremities. Several practical methods in current use provide relative orientation of segments either directly or as a derived parameter from measurements of relative position of segments. For example, electrogoniome-

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