Reliability and Validity of Measurement Using Smartphone-Based Goniometer of Tibial External Rotation Angle in Standing Knee Flexion

  • Jeon, In-Cheol (Dept. of Physical Therapy, The Graduate School, Yonsei University) ;
  • Kwon, Oh-Yun (Dept. of Physical Therapy, College of Health Science, Yonsei University, Dept. of Ergonomic Therapy, The Graduate School of Health and Environment, Yonsei University) ;
  • Weon, Jong-Hyuck (Dept. of Physical Therapy, College of Tourism & Health, Joongbu University) ;
  • Ha, Sung-Min (Dept. of physical Therapy, Division of Health Science, Baecseok University) ;
  • Kim, Si-Hyun (Dept. of Physical Therapy, The Graduate School, Yonsei University)
  • Received : 2013.03.08
  • Accepted : 2013.04.28
  • Published : 2013.05.21


The purpose of this study was to assess the intra-rater test-retest reliability of tibial external rotation angle measurement using a smartphone-based photographic goniometer, DrGoniometer (DrG) compared to a three-dimensional motion analysis system (Vicon). The current study showed an interchangeable method using DrG to measure the tibial external rotation angle in standing knee flexion at $90^{\circ}$. Twelve healthy subjects participated in this study. A rest session was conducted 30 minutes later for within-day reliability and five days later for between-day intra-rater test-retest reliability. To assess the validity of the measurement using DrG, we used a three dimensional motion analysis system as a gold standard to measure the angle of tibial external rotation. Intra-class correlation coefficient (ICC) and the standard error of measurement (SEM) values were used to determine the within- and between- day intra-rater test-retest reliability of using DrG and a three dimensional motion analysis system. To assess validity, Pearson correlation coefficients were used for two measurement techniques. The measurement for tibial external rotation had high intra-rater test-retest reliability of within-day (ICC=.88) and between-day (ICC=.83) reliability using DrG and of within-day (ICC=.93) and between-day (ICC=.77) reliability using a three-dimentional motion analysis system. Tibial external rotation angle measurement using DrG was highly correlated with those of the three-dimensional motion analysis system (r=.86). These results represented that the tibial external rotation angle measurement using DrG showed acceptable reliability and validity compared with the use of three-dimensional motion analysis system.



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