This article reviews the changing modes of failure in total knee arthroplasty over the past decade. Reasons for failure include polyethylene wear, aseptic loosening, instability, infection, arthrofibrosis, malalignment, or malposition, deficient extensor mechanism, periprosthetic fracture, and isolated patellar resurfacing. Awareness of the modes of failure may lower the prevalence of failure and aid in developing designs and techniques to better address the problems.