Between 1989 and 1993, 31 patients who had undergone ACL reconstruction using autogenous patellar bone-tendon-bone were studied to evaluate the effects on knee joint function. After having harvested the central one third of the patellar tendon, it was positioned isometrically through tunnels of tibia and femur and also central defect of the patellar ligament was sutured loosely. Clinically Hospital for special surgery(HSS) knee socre by Marshall 1997, manual knee test, knee extention and flexion angles, Cybex test, KT-2000 measurments and radiological study were performed for subjective and objective symptoms at the average follow-up 33 months (range 18-72 months). Quadriceps weakness of strength less than 80% of the normal side was present in 61% of patients, patellofemoral joint pain in 15%, AP translation more than 3mm in 23%, flexion contracture of 5 degree or more in 29%. Hospital for special surgery(HSS) knee score was improved from 35 to 46 in average during follow-up period. The height of the patella was increased in 2 cases and decreased in 6 cases within normal variation which was not significant statistically. The above results indicate that importance of postoperative rehabilitation program and extension position of knee joint after surgery place a major emphasis on the avoidance of flexion contracture and on the improvement of joint function.