title: The measurement of in vivo joint angles during a squat using a single camera markerless motion capture system as compared to a marker based system.
abstract: Markerless motion capture may have the potential to make motion capture technology widely clinically practical. However, the ability of a single markerless camera system to quantify clinically relevant, lower extremity joint angles has not been studied in vivo. Therefore, the goal of this study was to compare in vivo joint angles calculated using a marker-based motion capture system and a Microsoft Kinect during a squat. Fifteen individuals participated in the study: 8 male, 7 female, height 1.702±0.089m, mass 67.9±10.4kg, age 24±4 years, BMI 23.4±2.2kg/m(2). Marker trajectories and Kinect depth map data of the leg were collected while each subject performed a slow squat motion. Custom code was used to export virtual marker trajectories for the Kinect data. Each set of marker trajectories was utilized to calculate Cardan knee and hip angles. The patterns of motion were similar between systems with average absolute differences of <5 deg. Peak joint angles showed high between-trial reliability with ICC>0.9 for both systems. The peak angles calculated by the marker-based and Kinect systems were largely correlated (r>0.55). These results suggest the data from the Kinect can be post processed in way that it may be a feasible markerless motion capture system that can be used in the clinic.
authors.affiliation: Division of Physical Therapy, University of Kentucky, United States.
authors.forename: Anne
authors.initials: A
authors.lastname: Schmitz
authors.affiliation: Department of Computer Science, University of Kentucky, United States.
authors.forename: Mao
authors.initials: M
authors.lastname: Ye
authors.affiliation: Division of Physical Therapy, University of Kentucky, United States.
authors.forename: Grant
authors.initials: G
authors.lastname: Boggess
authors.affiliation: Department of Kinesiology and Health Promotion, University of Kentucky, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Shapiro
authors.affiliation: Department of Computer Science, University of Kentucky, United States.
authors.forename: Ruigang
authors.initials: R
authors.lastname: Yang
authors.affiliation: Division of Physical Therapy, University of Kentucky, United States. Electronic address: b.noehren@uky.edu.
authors.forename: Brian
authors.initials: B
authors.lastname: Noehren
mesh_terms: D000328:Adult; D005260:Female; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D014741:Video Recording / Q000295:instrumentation*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Hip and knee angles; Kinect; Markerless motion capture; Squat