Method for Estimating Three-Dimensional Knee Rotations Using Two Inertial Measurement Units: Validation with a...

Area of Science:

• Biomechanics
• Human Movement Analysis
• Wearable Technology

Background:

• Three-dimensional (3D) knee rotations are critical indicators of knee health and performance across various domains.
• Traditional optical motion capture for knee rotation analysis is confined to laboratory settings.
• Wearable inertial measurement units (IMUs) present a potential solution to overcome these limitations.

Purpose of the Study:

• To develop and present a novel method for estimating 3D knee rotations using IMUs.
• To rigorously benchmark the accuracy of the proposed IMU-based method against a high-precision instrumented mechanical linkage.

Main Methods:

• Utilized data from IMUs placed on the shank and thigh.
• Implemented a vector constraint for the knee's medial-lateral axis during hinge-like motion.
• Validated the method using optical encoders simulating pure and combined knee rotations (flexion/extension, internal/external rotation, abduction/adduction).

Main Results:

• The IMU-based method demonstrated high accuracy in estimating 3D knee rotations.
• Root-mean-square (RMS) error was consistently below 4 degrees.
• Correlation coefficients (r) between IMU estimates and truth data were greater than or equal to 0.94.

Conclusions:

• The developed IMU-based method provides a reliable and accurate approach for estimating 3D knee rotations.
• This technology has significant potential for real-world applications in monitoring knee health and performance outside the lab.