Measurement of SNQ. SNQ for ACL graft was calculated using the formula as followed: SNQ = (graft signal—PCL signal) / background signal. Signal intensity was measured with 15 ~ 20 cm2 circular ROIs on T2-weighted sagittal view. The graft signal was measured in its intra-articular portion at superior, middle, and inferior sites in the central slice of ACL. The average was calculated. The signal from the PCL was measured in its distal attachment. The background signal was measured 2 cm anterior to the patellar tendon via the same sagittal image slice. (SNQ signal/noise quotient, ACL anterior cruciate ligament, PCL posterior cruciate ligament, ROI regions of interest)