ObjectiveTo explore the relationship between anterior cruciate ligament (ACL) reconstruction failure and medial meniscus injury and decide whether medial meniscus injury could be the judgment index for ACL reconstruction failure without trauma history. MethodsBetween March 2011 and December 2015, 117 patients underwent ACL reconstruction, and the clinical data were analyzed retrospectively. All patients had no trauma history after ACL resconstruction. MRI examination showed medial meniscus injury in 56 cases (observation group) and no medial meniscus injury in 61 cases (control group). There was no significant difference in gender, age, side, reconstructive surgery, and follow-up time between 2 groups (P>0.05). The KT-2000 arthrometer was used to measure the difference value of tibial anterior displacement between two knees in 30° knee flexion. Then wether the ACL reconsruction failure was judged according to the evaluation criteria proposed by Rijke et al. ResultsIn observation group, the difference value of tibial anterior displacement was <3 mm in 7 patients, 3-5 mm in 11 patients, and >5 mm in 38 patients. In control group, the difference value of tibial anterior displacement was <3 mm in 31 patients, 3-5 mm in 18 patients, and >5 mm in 12 patients. The ACL reconstruction failure rate of observation group (67.9%) was significantly higher than that of control group (19.7%) (χ2=27.700, P=0.000). ConclusionAfter ACL reconstruction, medial meniscus injury occurs under no trauma history circumstances, indicating ACL reconstruction failure.