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Although one talks mostly of a medial and a lateral facet, the patella has in fact seven facets - the medial and lateral facets are each divided into three parts and there is a seventh facet (the odd facet) medial to the others.
Quick overview of the kneecap anatomy.
Arthroscopic Patellar Lateral Facetectomy. Ferrari MB, Sanchez G, Chahla J, Moatshe G and LaPrade RF. Arthrosc Tech. 2017 Apr; 6(2): e357–e362.