There are several normal anatomical variants associated with the patella, the most common being the accessory ossification centre(s). This page considers the plain film appearances of normal anatomical variants associated with the patella and how they can be distinguished from pathological appearances.

The patella usually ossifies from a single ossification centre, but can ossify from 2 or 3 ossification centres resulting in a bipartite or tripartite patella respectively.
A bipartite patella can be classifies as follows.