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Reliability and concurrent validity between two-dimensional and three-dimensional evaluations of knee valgus during drop jumps

Authors Ortiz A, Rosario-Canales M, Rodríguez A, Seda A, Figueroa C, Venegas-Ríos H

Received 10 November 2015

Accepted for publication 11 March 2016

Published 27 May 2016 Volume 2016:7 Pages 65—73


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 4

Editor who approved publication: Prof. Dr. Andreas Imhoff

Alexis Ortiz1,  Martin Rosario-Canales2,3,  Alejandro Rodríguez3, Alexie Seda3, Carla Figueroa3, Heidi L Venegas-Ríos4

1School of Physical Therapy, Texas Woman’s University, Houston, TX, 2Department of Anatomy & Neurobiology, 3Department of Physical Therapy, University of Puerto Rico, Medical Sciences Campus, San Juan, PR, 4School of Nutrition & Food Sciences, Texas Woman’s University, Houston, TX, USA

Purpose: The aim of this study was to establish the concurrent validity and reliability of four different two-dimensional (2D) video-based techniques for quantifying frontal plane knee kinematics during a 40 cm double-legged drop jump.
Participants and methods: A convenience sample of 16 healthy participants (nine males and seven females; age: [mean ± standard deviation] 25.5±2 years; body mass index: 24.33±2.98 kg/m2) participated in this investigation. A total of five trials during a 40 cm drop jump maneuver with a countermovement jump were used as the functional task. Four knee valgus measures, such as two different frontal plane projection angle measures, knee-to-ankle separation ratio (KASR), and knee separation distance (KSD), were measured using 2D and three-dimensional (3D) systems. To generalize to the greater population of possible evaluators, the testers performing the biomechanical analyses were three novice physical therapists. Intra- and intertester intraclass correlation coefficients (ICCs) were estimated for 2D analysis variables. ICCs were estimated for all measures between systems to determine concurrent validity of the 2D system.
Results: All four 2D measures showed good to excellent reliability (ICC: 0.89–0.99). KASR and KSD showed excellent correlation (ICC: 0.96; 95% CI: 0.82–0.98 and ICC: 0.94; 95% CI: 0.90–0.96, respectively) with the 3D system, while both methods of frontal plane projection angle showed poor to moderate correlation (ICC: 0–0.57) with the 3D system.
Conclusion: 2D KASR and KSD measures are cost effective, reliable, and highly correlated with the same measures using 3D techniques for the evaluation of knee valgus.

Keywords: Dartfish, Vicon, motion analysis, correlation

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