Abstract
We developed a device for treating stiff knees to increase the range of motion (ROM). To control below-knee active movement, a hybrid control system was employed. The system can switch two control modes according to torque angle characteristics that were observed by physical therapists (PTs) during the knee flexion ROM exercise. Angle control is adopted for the movement range and return range, while torque control is adopted for the pressure range. The knee flexion exercise using the device was performed in six patients, alternating between manual repetitive movement given by PT and automatic repetitive movement using the device every other day. The number of times of movement was repeated was eighteen for both sides. Load torque, ROM, and pain scale ratings were measured and compared between the first and 18th repetitions, and between manual and automatic operations at three stages: when the measurements were started, two weeks later, and at completion of measurement. ROM results showed a significant increase at the 18th repetition compared to the first repetition in all three stages for both manual and automatic bending movements. No differences were found between the two operations. The load torque value increased with time for both manual and automatic operations. With manual exercises, the torque showed a tendency to increase every time knee flexion movements were repeated. The pain scale ratings showed no significant difference between manual and automatic movements, but a score of the 18th repetition was significantly lower compared to the first repetition for automatic exercises at completion of measurements. These results suggest that the therapeutic device for treating stiff knees developed in this study provide the same effects to increase ROM at the same pain level as the manual ROM exercise given by PTs, and may play a significant role in general clinical use.
