Objective To compare the clinical effects of two pie-crusting technique in the treatment of posterior horn of medial meniscus tear.Method: From January 2016 to June 2018, 56 knees underwent arthroscopic partial meniscectomies for posterior horn of medial meniscus tear，who were divided into group outside-in and group inside-out according to the different techniques of medial collateral ligament release.The Lysholm score and MRI were used for evaluation of the outcomes．Results: All the 56 patients underwent successful surgical procedures and were followed up without complications.However,saphenous nerve injury，the great saphenous vein injury and infection in group outside-in were higher than that of group inside-out.The operation time of group outside-in was lower than that of group inside-out,the difference were statistically significant (P<0.05).MCL injury of group inside-out was lower than that of group outside-in，the difference were statistically significant (P<0.05 ) .However，the MCL of two groups healed well at postoperative 1months，the difference was no statistically significant ( P＞0.05) .To the latest follow up,the patients of group outside-in got statistically significant increases of Lysholm score from (49.12±1.19) before operation to ( 79.96±1.60) at the latest follow up ,and statistically significant increase of group inside-out from (48.70±0.94) preoperatively to (81.03±1.52) at the latest follow up.The MRI showed that there was no meniscus nonunion in both groups,the difference was no statistically significant (P＞0.05) .Conclusions: The outside-in and inside-out pie-crusting medial collateral ligament technique have good short-term effect in the treatment of posterior horn of medial meniscus tear .