As the total number of knee arthroplasties increase, the frequency with which periprosthetic fractures will be encountered can be expected to increase as well. The classification of these fractures is an important aspect in the development of an understanding of these problems. Adequate classification systems allow accurate communication between researchers and comparisons to be made between different techniques. Classification systems also allow algorithms to be developed to guide clinicians in the diagnosis, investigation, and treatment of these fractures. The authors present an outline of the classification systems described for fractures occurring in relation to total knee arthroplasty.