Table 1.

Comparison of the means and standard deviations of parameters measured on MRI or ultrasound in the neutral position and in 20° internal rotation. The Pearson’s correlation coefficient is listed for correlations between ultrasound and MRI

	MRI	Ultrasound in neutral position	Ultrasound in 20° internal rotation
AFD (anterior femoral distance)	4.6 ± 1.7	6.8 ± 3.8	6.2 ± 3.1
		0.346 (p < 0.033)	0.491 (p < 0.002)
Anterior offset	7.1 ± 2.2	10.8 ± 3.6	8.7 ± 3.1
		No correlation	No correlation
Offset ratio	0.16 ± 0.05	0.25 ± 0.07	0.20 ± 0.07
		No correlation	0.428 (p < 0.008)
Ratio AFD/ anterior offset	0.72 ± 0.35	0.66 ± 0.35	0.74 ± 0.36
		0.561 (p < 0.0001)	0.693 (p < 0.0001)