Joint angles tracking for rehabilitation at home using inertial sensors: a feasibility study

Joint angles are commonly measured in physical rehabilitation to evaluate joint function. Evidences showed that wearable inertial sensors can accurately quantify human motion information, however, the most advanced and accurate methodologies require the execution of complex calibration movements which are unsuitable to inexpert users and inadequate for a home context. This way, four different joint angles estimation methods requiring no calibration movement were developed in order to track the main human body joint angles in real time. IMUs mounted in bracelets were used to restrict sensor positioning on the limbs. For six different exercises, the estimated absolute and relative joint angles were evaluated against the marker-based video tracking software Kinovea ground-truth. Correlation analysis between estimated and ground-truth joint angles indicated a very strong and statistically significant correlation. The average error in estimated joint angles is below 5 degrees for all four methods employed, which may be an acceptable result for the rehabilitation at home scenario.