The purpose of this study was to evaluate the clinical outcome of total knee arthroplasty and analyze the prognostic factors in patients with stiff knees. Thirty-two patients (39 knees) with severe knee arthritis and an arc of motion of 50° or less were treated by total knee arthroplasty. The mean follow-up period was 58 months (range, 24-123 months). The mean arc of motion improved from 35° before the operation to 94° at the time of the latest follow-up (P<.05). Improvement in knee motion after postoperative 3 months was insignificant. The most important factor related to the final arc of knee motion was preoperative arc of knee motion. The V-Y quadricepsplasty was associated with an inferior clinical outcome. Total knee arthroplasty in patients with stiff knees has substantially improved in the clinical outcome and the arc of motion.