Abstract
Three-dimensional rotations across the human knee serve as important markers of knee health and performance in multiple contexts including human mobility, worker safety and health, athletic performance, and warfighter performance. While knee rotations can be estimated using optical motion capture, that method is largely limited to the laboratory and small capture volumes. These limitations may be overcome by deploying wearable inertial measurement units (IMUs). The objective of this study is to present a new IMU-based method for estimating 3D knee rotations and to benchmark the accuracy of the results using an instrumented mechanical linkage. The method employs data from shank- and thigh-mounted IMUs and a vector constraint for the medial-lateral axis of the knee during periods when the knee joint functions predominantly as a hinge. The method is carefully validated using data from high precision optical encoders in a mechanism that replicates 3D knee rotations spanning (1) pure flexion/extension, (2) pure internal/external rotation, (3) pure abduction/adduction, and (4) combinations of all three rotations. Regardless of the movement type, the IMU-derived estimates of 3D knee rotations replicate the truth data with high confidence (RMS error and correlation coefficient).
Highlights
The human knee is susceptible to injury from multiple mechanisms including, for example, hyperextension, over-use, and direct impact
The angle measured by the optical encoder about the base axis is differentiated with respect to time yielding an angular velocity signal to compare with those measured by the thigh and shank inertial measurement units (IMUs)
This section contains both qualitative and quantitative comparisons and discussions of the angles estimated using IMU data and the truth data obtained from the coordinate measurement machine (CMM)
Summary
The human knee is susceptible to injury from multiple mechanisms including, for example, hyperextension (including varus and valgus components), over-use, and direct impact (see, for example, [1,2]). The three-dimensional rotations across the knee (flexion/extension, internal/external rotation, and abduction/adduction) serve as important markers of knee health and performance and in multiple contexts such as human mobility, worker safety and health, athletic performance, and warfighter performance. Many biomechanical analyses incorporate measurements of knee rotations including studies of the long-term effects from knee injuries [7,8], Sensors 2017, 17, 1970; doi:10.3390/s17091970 www.mdpi.com/journal/sensors. Sensors 2017, 17, 1970 joint disorders including arthritis [9] and age- and gender-related differences in knee health [10]. Researchers have explored the effects of load carriage related to fall prevention [11], metabolic cost during walking [12,13], and warfighter performance during walking [14]. Unconstrained walking gait over ground differs from gait employed while walking on a treadmill [15]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
