DEVELOPMENT OF MOBILE SENSORS FOR MEASUREMENT OF KNEE MOTION AND APPLICATION IN PATIENTS WITH KNEE OSTEOARTHRITIS

Abstract

The Application of Inertial Measurement Unit (IMU) sensor is a new method to measure the kinematics of human movement. This IMU sensor, which consists of a triple-axis accelerometer, a triple -axis gyro sensor and a triple -axis magnetometer, is used to develop the mobile device using the knee joint angle measurement. In the present study, I developed the “IMU devices” and the “Knee Angle Recorder” software to cooperate with the four IMU devices. These IMU devices linked to a computer by the wireless connection. The benefits of the IMU devices via the wireless connection were the ambulatory devices, no restriction on the leg movement, and the real-time reporting of the knee movement. The software called the “Knee Angle Analyzer” was developed for the data analysis from the IMU measurement. However, the accurate data onto the measuring device are the awareness, hence, the accurate tests for the measuring angles by the developed “IMU devices” were this purpose. Also, any potential problems in the knee joint angle measurement were evaluated for this IMU system. All developed “IMU devices” had the inclined sensor from the zero line to be less than ±1 degrees. The accurate data onto IMU measurement were tested for the static and the dynamic conditions. The IMU devices were separated into two pairs and also were tested for the sagittal and the coronal planes. The results showed the root mean square (RMS) of different angles and the Intraclass Correlation Coefficient (ICC) values on the comparisons in the static condition between the reference angles and the IMU measurements to be less than 2 degrees (ICC≥0.99). The RMS of different angles and the ICC values when compared the measuring angles in the dynamic condition between the IMU system and the Qualisys system were less than 3 degrees (ICC≥0.98). Moreover, the “IMU devices” were tested for the accuracy on the knee joint angle measurement during the knee functional movements with ten healthy participants. The four functional knee movement tests (the knee flexion test, the hip and knee flexion test, the forward step test and the leg abduction test) and the walking test were used to compare the knee joint angles between the IMU system and the Qualisys system. The results showed the RMS of different angles and the ICC values to be less than 6 degrees (ICC≥0.85) for the knee flexion-extension movement during the knee flexion test, hip and knee flexion test and the forward step test. For the walking test, the RMS of different angles and the ICC values were less than 6 degrees (ICC≥0.84) on the knee flexion-extension movement in the gait cycle. The results from the leg abduction test revealed this IMU system to be the unable usage for measuring the knee abduction-adduction movement. Finally, the IMU system was applied to measure the pattern of knee flexion-extension movement and the kinematic variables by the forty elderly women with and without symptomatic knee osteoarthritis during the walking. The IMU system could detect some differences on the kinematic variables between the symptomatic sides and non-symptomatic sides and the differences between two groups of participants. In conclusion, these developed “IMU devices”, the “Knee Angle Recorder” software, and the “Knee Angle Analyzer” software could be used for the measurement of knee flexion-extension movement.