Purpose:To evaluate the clinical outcome in patients who received anterior cruciate ligament (ACL)reconstruction via anteromedial portal with or without posterior wall blowout.Methods:Twenty patients with ruptured ACL,who have received ACL reconstruction via anteromedial portal between Apr 2012 and Oct 2013 were enrolled.According to the conditions of posterior wall,the patients were divided into 2 groups:posterior wall blowout group (10 patients) and posterior wall intact group (10 patients).The median follow up time were 63 (range 19 75) months and 60.5 (range 25-64)months in the 2 groups respectively.The clinical outcome was evaluated by knee joint physical examination,magnetic resonance imaging (MRI),the Intational Knee Documentation Committee (IKDC)2000 subjective score,Lysholm score,Tenger score,difference of thigh circumference,KT-2000 and Biodex isokinetic dynamometer system.Results:No significant differences were found in terms of the IKDC score,Lysholm score,Tegner score,Lachman test positive rate or Pivot Shift test positive rate between the two groups.In KT-2000 and Biodex isokinetic dynamometer tests,the difference of muscle strength between affected knees and unaffected knees in posterior wall blowout group was not significant less than that of posterior wall intact group (p ＞ 0.05).In addition,there is no statistical difference between the two groups in signal/noise quotient (SNQ) of the graft (p ＞ 0.05) in post operative MRI.Conclusion:Blowout of posterior wall in ACL reconstruction via anteromedial portal does not affect the clinical outcome as long as reliable fixation has been taken intraoperatively.