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Table 1 Intra-rater reliability of the visual FPI, Kinect and Vicon systems for each item of the FPI

From: Reliability and validity of the Microsoft Kinect for evaluating static foot posture

  FPI Kinect Vicon
FPI 1 Talar head    
  Day 1 median (IQR) 0 (0 to 1)   
  Day 2 median (IQR) 1 (0 to 1) N/A N/A
  Spearman’s rho 0.38*   
FPI 2 Lateral curvature    
  Day 1 median (IQR) 0 (0 to 1) −1.55 (−3.40 to 0.75) −1.32 (−5.06 to 0.93)
  Day 2 median (IQR) 0 (0 to 1) −0.97 (−4.29 to 0.74) −2.83 (−4.06 to 0.51)
  Spearman’s rho 0.52* 0.78* 0.73*
FPI 3 Calcaneal inv/ev    
  Day 1 median (IQR) 0 (0 to 1) 10.03 (7.54 to 11.71) 9.77 (6.82 to 12.98)
  Day 2 median (IQR) 1 (0 to 1) 11.34 (9.32 to 14.26) 10.73 (7.57 to 12.18)
  Spearman’s rho 0.42* 0.30 0.37
FPI 4 TNJ bulging    
  Day 1 median (IQR) 1 (0 to 1) −17.00 (−22.00 to −13.00) −12.93 (−15.86 to −8.52)
  Day 2 median (IQR) 1 (0 to 1) −16.50 (−19.25 to −13.00) −11.63 (−16.22 to −8.71)
  Spearman’s rho 0.17 0.62* 0.79*
FPI 5 Congruence of MLA/Arch height  
  Day 1 median (IQR) 1 (0 to 2) 49.35 (39.94 to 61.36) 26.75 (22.19 to 31.12)
  Day 2 median (IQR) 1 (0 to 1) 46.28 (40.33 to 58.88) 28.82 (23.86 to 32.72)
  Spearman’s rho 0.63* 0.72* 0.78*
FPI 5 Arch peak    
  Day 1 median (IQR)   17.65 (15.69 to 32.65) 42.67 (38.25 to 45.03)
  Day 2 median (IQR) N/A 24.20 (15.56 to 35.76) 42.41 (34.59 to 46.53)
  Spearman’s rho   0.66* 0.13
FPI 6 Forefoot ab/add    
  Day 1 median (IQR) 1 (0 to 2) −3.00 (−6.00 to 3.00) 2.87 (−0.71 to 7.88)
  Day 2 median (IQR) 1 (0.75 to 1) 0.00 (−6.00 to 6.50) 4.19 (−1.15 to 8.75)
  Spearman’s rho 0.29 0.21 0.55*
FPI total score    
  Day 1 median (IQR) 3 (2 to 6)   
  Day 2 median (IQR) 4 (2 to 5.25) N/A N/A
  ICC 0.87*   
  1. Note: * p < 0.05; FPI = Foot Posture Index; IQR = interquartile range; TNJ = talo-navicular joint; MLA = medial longitudinal arch; ICC = Intraclass correlation coefficient.