Fig. 4

Axial fat-saturated T2-weighted MR image for assessment of the trochlear; a line was drawn tangential to the posterior aspect of the femoral condyles and was considered as a reference line (line D). The lines were drawn perpendicularly to the (line D) and indicated the longest anteroposterior diameters of the lateral (line A) and medial (line C) trochlear facets and the deepest point of the trochlear groove (line B). The femoral trochlear depth was calculated as (A + C/2) – B. A trochlear depth of 3 mm or less was considered as an indicator of trochlear dysplasia [9]