In this study we used the techniques of nonlinear dynamics to analyze the s
tability of normal and pathological gait in children, We based the analysis
on the assumption that a human at steady-state locomotion can be represent
ed as a nonlinear periodic system. Kinematic data for the lower limb joints
were used to construct phase plane portraits and first return maps for the
hip, the knee and the ankle joints. Anomalies in the joint rotations of pa
thological individuals were graphically depicted by comparing the phase pla
ne portraits and first return maps. Using the Floquet theory, an index of d
ynamic stability was used to compare normal and pathological gait. (C) 2001
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