AbstractChronic flexion contracture of the knee is difficult to treat, especially in cases with long‐standing extension deficits and with generalised arthrofibrosis. We present a technique combining arthroscopic or open anterior debridement with a posterior capsulotomy. This capsulotomy is performed via a posteromedial incision and a posteromedial arthrotomy. All scar tissue is resected, and the entire posterior capsule is detached from its femoral attachment. Of 24 patients treated with arthroscopic arthrolysis and posterior capsulotomy from 1989 to 1993, 21 were reviewed with a mean follow‐up of 18 months (range 6–38 months). The mean extension deficit preoperatively was 17° (range 10–30°), and symptoms had persisted from 6 months to 7 years. Extension improved to a mean value of 2°; no patient had more than 5° of extension deficit at follow‐up. The knee function improved significantly (Lysholm Score preoperative 62, postoperative 88, Tegner Scale preoperative 2.2, postoperative 4.0). No neurovascular complications were observed, and we conclude that posterior capsulotomy is a safe and efficient adjunct procedure to anterior arthrolysis and is indicated in cases with chronic flexion contracture.