Cerebral palsy (CP) affects 0.25% of newborn babies in the U.S. alone each year. Hypertonia (increased joint resistance to externally imposed motion) is a common symptom that limits function in this patient population. It may originate in spasticity, dystonia or rigidity or may be a combination of all these factors. Surgical, rehabilitation and pharmacotherapeutic methods are used to improve functional outcome in patients with cerebral palsy. These treatments are not always effective, and the amount of improvement is difficult to predict. The choice of treatment is based on clinical tests that are not objective, especially in children, and they do not allow for differentiation between various causes of increased joint resistance. As a result, ineffective treatments are offered to patients with different types of movement disorders. The complex torque devices used in research facilities to quantify the resistance of a joint cannot be easily applied in clinical settings. In previous studies, a portable measurement method was developed based on a hand-held force transducer, which allowed for the quantification of biomechanical and bioelectrical characteristics of resistance of a knee joint at different velocities. Using this method, we found different types of hypertonia that had not been previously reported in patients with cerebral palsy. It is not clear to what degree hypertonia restricts an ability to execute selected functional tasks, due in part to the considerable variability in patients with CP. If this variability could be decreased, the relationship between restricted ability and the different types of hypertonia would be easier to determine. Strong arguments exist to consider different pathophysiologies in these different types of hypertonia.