Passive dynamics of the knee joint in healthy children and children affected by spastic paresis

Objective. The purposes of this study were (1) to evaluate how changes in b iomechanical parameters affect segment dynamics in children and (2) to dete rmine whether the biomechanical parameters were changed in children with sp astic paresis. Design. In vivo measurements were collected of knee viscoelastic properties . Background It is unknown if the inertial and viscoelastic properties of a h uman growing limb should be considered in motor performance. Also unclear a re whether changes in passive dynamics might be responsible for abnormal co ntrol in human spastic paresis. Method. Small oscillation techniques were used to measure moment of inertia of lower leg, stiffness and viscous damping of the knee joint. Eighty seve n healthy children and 32 children with spastic paresis participated. Resul ts. Moment of inertia, stiffness and the damping changed with the fifth pow er of child's height. Dynamic equation of motion parameters were a constant , independent of the child's height. Passive viscoelastic parameters were n ot changed in spastic patients. Conclusions. Inertial and viscoelastic properties of a growing limb segment should not be considered in motor performance. Passive viscoelastic proper ties were not changed in patients with spastic paresis and, therefore, cann ot be responsible for abnormal control in human spastic paresis.