PCL resists 95% of posterior drawer force and the proposed function of PCL are resists posterior drawer, resists hyperextension, limits internal rotation, limits hyperextension and prevents varus and valgus. Although numerous procedures have been described for reconstruction of the PCL, but remain still great controversy as to the best method. Clancy reported natural history of 124 PCL insufficiency. Degenerative change was noted mainly on medial femoral condyle with time, all three compartments were involved. Reconstruction of old PCL injury was divided into extraarticular & intraarticular group. The intraarticular lig. Reconstruction was a reliable method to correct the rotational axis of knee joint instability. Authors reviewed 17 case in 17 patients who were treated by recontruction of PCL with patellar tendon under arthroscopy from March, 1988 to June, 1989. The follow-up was over 12 months. The clinical result according to Clancy, excellent in 4 cases, good in 8 cases, Fair in 3 cases, and failure in 2 cases. Associated injuries of the knee joint were noted on 12 knee, ACL rupture in 3 cases, meniscus tear in 3 cases, posterolateral instability in 2 cases, medical collateral ligament rupture in 2 cases and lateral collateral ligament rupture in 2 cases. We concluded that relatively acceptable result was obtained with arthroscopic reconstruction of old PCL injury using patellar tendon graft, and arthroscopic reconstruction needed another posteromedial portal for accurate positioning of tibial tunnel. And 9 cases needed central opening through patellar fat pad for accurate positioning of femoral tunnel and making the passage of graft easy.