Few reports address the reconstructive challenge of total knee arthroplasty after a surgically fused or ankylosed knee. The long term results and complications of a large series of patients who have had their ankylosed or arthrodesed knee converted to a total knee replacement were evaluated. Thirty-seven knees (35 patients, 28 female and 7 male) without any motion in the knee were retrospectively reviewed in a multicenter study after total knee arthroplasty. The mean age was 53 years, and the average length of followup was 90 months. The results at followup showed an average 7 degrees lack of extension and 62 degrees flexion. Complications included 24% short term complications and 35% major complications with a 14% infection rate. The total complication rate was 57%. A satisfactory outcome (no pain and an unlimited ambulation distance) was obtained in only 10 patients (29%). Patients with a satisfactory outcome had an average age of 45, and postoperative knee flexion of 87 degrees, significantly different from those with an unsatisfactory outcome. There was no relationship between results and the angle at which the knee was ankylosed preoperatively. This analysis indicates that although success in reconstructing a previously ankylosed or arthrodesed knee is possible, the lack of consistent adequate motion and the complication rate may suggest that the surgeon reconsider the risks and benefits of this difficult procedure.