Dynamics of children with torsional anomalies of the lower limb joints

In this study we used the techniques of nonlinear dynamics to analyze the stability of normal and pathological gait in children. We based the analysis on the assumption that a human at steady-state locomotion can be represented 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 pathological individuals were graphically depicted by comparing the phase plane portraits and first return maps. Using the Floquet theory, an index of dynamic stability was used to compare normal and pathological gait.