Background: Early detection and treatment of extensor mechanism rupture are essential for a long-term functional knee joint. In chronic cases, quadriceps muscle retraction and contracture make surgery difficult and results are less predictable. Objectives: The purpose of this study was to evaluate outcomes in the cases of late repaired patellar tendon rupture. Methods: This study included patients with chronic patellar tendon rupture who were operated at Shafa orthopedic hospital from 2006 to 2013. Results: A total of ten patients were evaluated, wirh 12 cases of chronic patellar tendon rupture. Patients had a mean age of 34. 4 years (range 18-58). Seven cases were caused by a traffic accident and three by a fall. The mean length of time from injury to surgery was 23 months (range 3-132). The mean time of follow-up was 6. 2 years (range 3-9). Cerclage wire reinforcements were applied in nine of the knees and three knees had fiber wire reinforcement. Tendon graft augmentation was applied in ten of the knees; six with semitendinosus and gracilis autograft, two with semitendinosus autograft, one with an Achilles tendon allograft, and one with a tibialis anterior allograft. Means for preoperative/postoperative active knee range of motion, extension lag, subjective international knee documentation committee score, and modified Cincinnati scores were 81/117, 32/2, 22. 7/84. 5 and 24/87, respectively. Wire breakage was seen on all nine knees but wires were removed in only two symptomatic cases. Conclusions: Good to excellent results were obtained in terms of functioning with operative treatment of chronic patellar tendon rupture. Direct repair with autogenous or allogenic graft augmentation and cerclage wire reinforcement and postoperative cast immobilization are recommended.