Development of Electrogoniometer with Sliding Arms for Measurement of Joint Angle

Abstract

It is difficult to obtain the accurate data of the joint motion by means of the conventional electrogoniometer with a fixed axis of rotation, because the joint has a migrating axis of rotation. This study was designed to develop the electrogoniometer which is able to measure the joint angle more accurately. The experiments were focused on measurement of the joint angle during knee flexion-extension. In order to determine the motion of the knee joint, the roentgenograms of the joint were taken at various positions during knee flexion-extension. It was confirmed that the axis of rotation migrated forward with knee flexion. Thus, new electrogoniometer provided with sliding arm structure was designed and constructed. The arms were extended and shortened by themselves with knee flexion-extension. To check the accuracy of the new electrogoniometer, the x-ray TV images of the knee joint wearing this goniometer were recorded continuously during flexion-extension In addition, the roentgenograms were taken simultaneously. These inspections clearly showed that the electrogoniometer followed the migration of the axis of rotation quite accurately, and the arms were kept parallel to tibia and femur, respectively. Judging from these results, it was validated that the new electrogoniometer was a reliable device to measure the knee joint angle with high degree of accuracy.