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J Biomech. 2014 Jan 22;47(2):587-91. doi: 10.1016/j.jbiomech.2013.11.031. Epub 2013 Nov 25.

Accuracy and repeatability of joint angles measured using a single camera markerless motion capture system.

Author information

1
Division of Physical Therapy, University of Kentucky, United States.
2
Department of Computer Science, University of Kentucky, United States.
3
Department of Kinesiology and Health Promotion, University of Kentucky, United States.
4
Division of Physical Therapy, University of Kentucky, United States. Electronic address: b.noehren@uky.edu.

Abstract

Markerless motion capture systems have developed in an effort to evaluate human movement in a natural setting. However, the accuracy and reliability of these systems remain understudied. Therefore, the goals of this study were to quantify the accuracy and repeatability of joint angles using a single camera markerless motion capture system and to compare the markerless system performance with that of a marker-based system. A jig was placed in multiple static postures with marker trajectories collected using a ten camera motion analysis system. Depth and color image data were simultaneously collected from a single Microsoft Kinect camera, which was subsequently used to calculate virtual marker trajectories. A digital inclinometer provided a measure of ground-truth for sagittal and frontal plane joint angles. Joint angles were calculated with marker data from both motion capture systems using successive body-fixed rotations. The sagittal and frontal plane joint angles calculated from the marker-based and markerless system agreed with inclinometer measurements by <0.5°. The systems agreed with each other by <0.5° for sagittal and frontal plane joint angles and <2° for transverse plane rotation. Both systems showed a coefficient of reliability <0.5° for all angles. These results illustrate the feasibility of a single camera markerless motion capture system to accurately measure lower extremity kinematics and provide a first step in using this technology to discern clinically relevant differences in the joint kinematics of patient populations.

KEYWORDS:

Accuracy and reliability; Joint angles; Microsoft Kinect; Motion capture

PMID:
24315287
DOI:
10.1016/j.jbiomech.2013.11.031
[Indexed for MEDLINE]

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