Neuromuscular modeling of spasticity in cerebral palsy.

Data from the pendulum knee test has been used to develop two active models that use external torques to closely match the experimental knee trajectories of subjects with spasticity due to cerebral palsy. These data were collected from three subjects who are identical triplets; two of whom have clinically measurable spasticity. A passive model that accurately describes the knee trajectory of the nonspastic subject serves as the passive plant for two active models. One of these models allows direct application of external torques, and the second provides additional torque as the result of velocity feedback. Both active models and the passive model use separate parameters of stiffness and damping for the agonist and antagonist muscles.