-Validation and reliability of knee kinematics and gait analysis using flexible wearable sensors

Purpose

Knee kinematics assessments are essential in healthcare, particularly in sports medicine, for evaluating joint motion. While opto-electronic motion capture systems like VICON remain the gold standard, they require large calibrated spaces, are expensive, and demand specialized training. To address these limitations, wearable motion capture systems have been introduced. However, their accuracy and consistency remain unclear. This study aims to validate the performance of the KIMIA Recover wearable system for assessing knee flexion-extension and gait cycle walking, comparing its accuracy against the VICON system.

Methods

Thirty (30) participants were enrolled in the study, performing two exercises—knee flexion-extension and walking—while their movements were recorded simultaneously by the KIMIA and VICON systems. The recorded signals were analyzed statistically to evaluate measurement accuracy. A novel calibration method was introduced to enhance the KIMIA system’s precision.

Results

The Root Mean Squared Error (RMSE) between the two systems was 4.43° ± 0.34° for flexion-extension and 4.21° ± 0.49° for walking. The Intraclass Correlation Coefficient (ICC) indicated strong agreement, with values of 0.96 ± 0.01 for flexion-extension and 0.86 ± 0.03 for walking.

Conclusions

The KIMIA system demonstrated high accuracy and consistency in measuring knee kinematics, making it a viable alternative to optical motion capture systems for real-world applications. The introduced calibration method further enhances its reliability, supporting its use in healthcare and sports medicine.