We compared the results of total knee arthroplasties in patients with stiff or ankylosed knees. We retrospectively reviewed 90 total knee arthroplasties in 52 patients with minimum 2 years followup who had less than a 50 degrees arc of flexion preoperatively. Preoperative and intraoperative data were retrieved from a computerized database. Patients were followed for an average of 6.5 years at an outpatient department. Knee Society knee scores improved from 34.6 points preoperatively to 89.5 points postoperatively in the stiff knees and from 47 points preoperatively to 75 points postoperatively in the ankylosed knees. The arc of flexion improved from 35 degrees -69 degrees preoperatively to 1 degrees -94 degrees postoperatively in the stiff knees and from 0 degrees to 3 degrees -77 degrees in the ankylosed knees. There were major complications in four of the 26 ankylosed knees and in two of the 64 stiff knees. The data suggest results of total knee arthroplasty are better in patients with stiff knees than in patients with ankylosed knees.