Low-cost intrinsic optical fiber FPI sensor for knee kinematic gait analysis and e-Health architecture

Analysis of gait pattern of individuals is a very useful tool for the identification of locomotive motor anomalies, which can lead to early diagnosis and adequate treatment of patients with motor disorders. The knees are the lower limb joints exposed to major tension during human locomotion, presenting higher risk of a wider range of possible disorders. The devices used to monitor human joints should be comfortable and not restrain patients’ movement, while maintaining their resolution and accuracy. Most of current measurement techniques are based on electronic devices, which are often not adequate for demanding environments, such as the context of physical rehabilitation. We propose an e-Health sensing solution to dynamically monitor human knee angles during gait, using low-cost intrinsic Fabry-Perot interferometers optical fiber sensors (FPI-OFS). To the best of our knowledge, no previous efforts have reported the use of FPI sensors for such dynamic monitoring. The overall sensor consists of an optical fiber containing the FPI microcavity, which is embedded along the longitudinal direction of a kinesio tape (K-Tape), and placed along the knee rotation axis. Since the K-Tape has great adhesion to the skin, the FPI sensor is kept at the knee rotation axis, without restricting the user’s movements. During the knee flexion/extension, the K-Tape extends/compresses accordingly, resulting in the modulation of the reflected spectrum by the FPI-OFS. Several calibration and performance tests have been performed. Their results show the reliability and accuracy of the proposed solution, with sensibilities values of 53.8±2.4 pm/°.