The trochlear groove of the anterior distal femur guides the movement of the patella during knee flexion, Dejour et al developed a classification for deformity of the trochlea (trochlear dysplasia) seen on imaging studies.
Trochlear Groove
Finding on Imaging Study
Trochlear Facets
Type
deep and concave
none
symmetrical
normal
shallower but symmetrical and concave
crossing sign on lateral X-ray
symmetrical
A
flat and convex
supra-trochlear spur
B
flat and convex
double contour sign
medial facet hypoplastic; lateral facet convex
C
flat and convex
all of the above
facet heights asymmetrical (cliff pattern)
D
The crossing sign occurs when the deepest part of the trochlea crosses the most anterior part of the lateral condyle.
The supra-trochlear spur (bump) represents a bulge of the proximal trochlea.
To read more or access our algorithms and calculators, please log in or register.
