Table 2.

The Dejour’s classification of trochlear dysplasia

Type	Sagittal View	Axial images
A (54%)	CS	Shallower trochlea
B (17%)	CS and SS	Flat or convex
C (9%)	CS and DC	Convex lateral facet and hypoplastic medial facet
D (11%)	CS, SS, DC	A prominent and convex lateral facet with a vertical connection (squared) to an hypoplastic medial facet almost absent (cliff pattern).

Cross-checking the radiographic sagittal view and the cross-sectional images is fundamental to include a patient within one of those trochlear types

CS Crossing sign, SS Supratrochlear spur, DC Double contour