Wiberg Type 1 patella
Wiberg Type 3 patellar dysplasia
Wiberg Type 4 patellar dysplasia
Classification of Patellar Dysplasia
The Wiberg classification of the shape of the patella, based upon the relative lengths of the facets, is widely used to describe different patellar shapes.
The patella morphology in trochlear dysplasia--a comparative MRI study. Fucentese SF, von Roll A, Koch PP, Epari DR, Fuchs B, Schottle PB. Knee. 2006 Mar;13(2):145-50.