Study aim: the aim of the study was to evaluate whether the use of instrumented versions of spasticity tests would provide us with clinically more useful information on the patient’s status. Material and methods: the study included 19 children, 8–17 years old: 7 girls and 12 boys. Pendulum, velocity, and popliteal tests were performed using the Vicon system (knee joint angle, 8 muscles EMG). Dynamic movement ranges of the knee joint during velocity and popliteal tests (ROM), indices of the pendulum test, and muscle activity in dependence of velocity of movement (MA, MAST) were calculated. Correlation coefficients between ROM, Vmax, MA, and MAST were calculated to show whether instrumentation of clinical tests can validate the patient’s status more precisely. Results: Vmax value from the pendulum test does not always correlate with ROM. Scores of MA and MAST do not correlate with ROM. Vmax generally does not correlate with MA or MAST. Conclusions: ROM is one of the most important parameters reflecting the level of spasticity but it is not sensitive enough to detect small changes in the patient’s status. In that case, Vmax of the pendulum test and the number of activated muscles in velocity and popliteal tests could become important tools to assess changes in spasticity level, especially when motion systems are more commonly available.