Quantitative analysis of the pendulum test: application to multiple sclerosis patients treated with botulinum toxin.

The aim of this study was to develop quantitative analytical methods in the application of the pendulum test to both normal and spastic subjects. The lower leg was released by a torque motor from different starting positions. The resulting changes in the knee angle were fitted by means of a time-varying model. Stiffness and viscosity coefficients were derived for each half-cycle oscillation in both flexion and extension, and for all knee starting positions. This method was applied to the assessment of the effects of Botulinum toxin A (BTX) in progressive multiple sclerosis patients in a follow-up study. About half of the patients showed a significant decrement in stiffness and viscosity coefficients.