Reasons for reoperation after knee revision surgery are implant loosening, sepsis, extensor mechanism problems, fractures of bone or prosthetic components, wear debris, and limited range of motion. The purpose of this study was to review the complications requiring reoperation in a large number of condylar revision total knee arthroplasties to determine the incidence and outcome after treatment. Six hundred fifty-five condylar revision total knee arthroplasties performed during a ten-year period were retrospectively reviewed. Forty-six knees without a history of arthroplasty infection required a total of 60 reoperations after the revision surgery. A reoperation was performed for extensor mechanism or patellar problems in 19 knees (41%), component loosening in ten knees (22%), deep infection in nine knees (20%), wound problems in nine knees (20%), tibiofemoral instability in eight knees (17%), limited range of motion in four knees (8%), and particulate debris synovitis in one knee (2%). All patients were observed for an average of 7.5 years. Twenty-four knees (52%) were considered clinical failures because of pain, limited motion, instability, and sepsis. Awareness of these failure modes may help to prevent complications by strict attention at the time of revision surgery to protection of the patellar tendon attachment and collateral ligaments, balancing of the extensor mechanism, preservation of the patellar blood supply, proper component position and sizing, restoration of the mechanical axis, and use of more constrained implant designs.