The posterior cruciate ligament is the primary static restraint to posterior translation of the tibia and provides proprioception within the knee. The goals of treatment in the injuries of PCL are restoration of normal tibiofemoral stability and reduction of long term osteoarthrosis of the knee. The purpose of this study is to cornpare functional outcome, muscle power, and posterior stability between conservative treatment and reconstruction with autogenous RPTB augmented with Kennedy LAD in PCL injuries. Twenty-seven patients with PCL rupture who have been treated from November 1990 to May 1996 were reviewed. The patiens were divided into conservative group and reconstruction group. Conservative treatment was done in 15 patients and reconstruction by autogenous bone patellar tendon bone with Kennedy LAD was performed in 12 patients. All patients were evaluated with posterior stress x-ray films, KT-2000 knee ligament arthrometer, Cybex 340 isokinetic dynamometer, subjective Cincinnati symptom rating scale and Lysholm knee score, complication. The results were as follows; 1. Mild and moderate posterior instability was remained in spite of BPTB graft and need more stable fixation technique and vigorous rehabilitation program. 2. At the angular velocity of 90 degree/sec and 180 degree/sec, the muscle strenth of quadriceps was decreased after PCL injury in both group in the test of Cybex 340 isokinetic exercises. The power of hamstrings were not changed after PCL injuries. 3. Average Lysholm knee score was 89 points in reconstruction group and 78 points in conservative group and average Cincinnati symptom-rating scale was 8.4 points in reconstruction group and 7.1 points in conservative group. More satisfied functional results and subjective symptoms were revealed in the reconstruction group and statiscal significancy (p<0.05) was showed when comparing conservative group with reconstruction poup. 4. Good clinical results did not always coincidence with lesser posterior instability and clinical results were influenced by associated injury of the knee. The more combined ligament injury of the knee, the worse clinical results.