There is a spectrum of articular surface involvement in multifragmentary articular fractures. They tend to fall into one of two patterns:
It is easy for the surgeon to miss a frontal plane fracture, or other fracture lines in the articular surface, and think that there is only a simple articular injury. In order to obtain an accurate reconstruction of the joint surface, it is important for the surgeon to appreciate the anatomy of the fracture lines. This requires careful study of the plain radiographs and obtain a CT-scan if there is any question.
The following x-ray shows an open fracture with an associated multifragmentary patellar fracture.