Revision Knee Arthroplasty in the Setting of a Deficient Extensor Mechanism

Extensor mechanism deficiency after total knee arthroplasty (TKA) is a devastating complication. The incidence of extensor mechanism disruption ranges from 0.17% to 4%. Although there is scant literature, the rate of deficiency is higher in the revision setting. The causes of extensor mechanism deficiency include quadriceps disruption, periprosthetic patellar fracture, and patellar tendon disruption. In the multiply operated knee, significant attenuation of the extensor mechanism can also lead to deficiency. Management of extensor mechanism deficiency is difficult and varies depending on the etiology. Treatment can range from nonoperative with immobilization to arthrodesis. This chapter will focus on the etiology, management, and controversies related to extensor mechanism deficiency. Lastly, this chapter will address tips and tricks for dealing with these issues, especially in the revision setting.