BACKGROUND: Primary motor cortex (M1) organization and quadriceps femoris excitability may change after anterior cruciate ligament injury (ACLi) and anterior cruciate ligament reconstruction (ACLr), as demonstrated by transcranial magnetic stimulation (TMS) studies. OBJECTIVE: To systematically review studies evaluating changes in quadriceps femoris corticospinal and intracortical excitability in subjects with ACLi and ACLr. METHODS: Database searches were conducted in PubMed, Embase, Scopus, and ScienceDirect, with the last search performed on November 23, 2023. Newcastle-Ottawa Scale and a specific checklist for evaluating descriptions in studies using TMS assessment were used. Continuous variables were expressed as mean and standard deviation and represented by the estimated difference from the mean and 95% confidence interval (CI). Heterogeneity was assessed by Chi RESULTS: Fourteen studies, comprising 381 individuals, using TMS were identified. Meta-analysis results showed significantly higher motor threshold (MT) in ACLi/ACLr individuals compared to healthy controls ( CONCLUSION: Quadriceps MT and SICI are altered in ACLi and ACLr populations, and minor alterations were identified in MEP, demonstrating brain changes related to anterior cruciate ligament injury and/or reconstruction.