A measure of spasticity based on the exponential fit of the knee joint torque estimated from the goniogram during the pendulum test

Pendulum test is a method to quantify the spasticity. We used the goniogram recorded during the pendulum test to estimate the knee joint torque based on the model which considers spastic reflex activity. We fitted the exponential curve Th = ae-bt to the estimated knee joint torque to calculate the parameters a and b. We compared the scaled value log a/b with the modified Ashworth score. We used 8 sets of data collected in a clinical study with six complete paraplegic subjects. The comparison shows that the ratio a/b correlates with the MAS scores; thereby, can be used as a measure of spasticity. The advantage of using the ratio a/b is that this score is not rater dependent and that the scores are real numbers compared the MAS scores; thereby, providing better resolution of the level of spasticity.