Angle of knee position [˚]

AM portal

relatively standard

deviation of radial distortion [%]

AL portal

relatively standard deviation of radial distortion [%]

TT portal

relatively standard deviation of

radial distortion [%]

30

no visibility

no visibility

0.95

50

0.68

1.24

0.68

70

1.46

1.20

0.54

90

1.10

1.27

0.15

110

0.40

1.18

0.15

130

0.10

0.70

0.08