summary TKA Extensor Mechanism Ruptures are traumatic periprosthetic injuries that consist of patellar tendon injuries or quad tendon injuries. Diagnosis can be made clinically in a patient with history of a TKA who is unable to perform a straight leg raise. Radiographs may show patella alta or patella baja. Treatment is generally surgical repair versus reconstruction depending on available patella bone stock and chronicity of injury. Epidemiology Incidence 0.17% to 2.5% Etiology Causes intraoperative avulsion from tibial tubercle postoperative manipulation impingement trauma Presentation Symptoms knee pain and weakness Imaging Radiographs patella alta or baja Treatment Nonoperative knee immobilizer x6 weeks indications partial quadriceps tendon rupture fracture of the patella in which the extensor mechanism remains intact Operative direct repair with suture indications partial patellar tendon avulsion (< 30%) primary repair and augmentation with graft indications complete laceration of patellar tendon with adequate patellar bone stock extensor mechanism reconstruction indications complete laceration of patellar tendon without adequate patellar bone stock and deficient soft tissues chronic extensor mechanism (patella or quadricep tendon) disruption reconstruction with synthetic polypropylene (ie. Marlex mesh) has been shown to have similar clinical outcomes at a lower cost than allograft techniques reconstruction with synthetic polypropylene is recommended in patients with immune-compromise knee arthrodesis indications salvage option for multiple failures of extensor mechanism reconstruction, especially if complicated by infection