This can be a simple break into two parts, or a comminuted fracture, where the kneecap is smashed into three or more parts.
It is really important to see an expert after a patellar fracture, because arthritis may be triggered behind the kneecap if the broken fragments are not properly re-aligned after the injury. The surgeon will look for 'displacement', that is he/she will look on the X-ray to see if the fragments are still in good contact or whether the impact has forced the fragments apart.
Displaced fragments may be pulled closer together with a cerclage wire, a wire that is passed in a circle around the outer aspect of the kneecap.
Follow-up X-rays will be necessary to determine how well the fragments remain aligned and whether healing of the bone has occurred.