PURPOSE: The purpose of this study was to compare the lower extremity Y-balance results of the operative and uninjured limbs in ACLR patients cleared to return to sports. METHODS: In this IRB-approved study, we analyzed prospectively collected data on patients undergoing primary ACL reconstruction at our academic medical center. Patients who were cleared by their orthopaedic surgeon and/or rehabilitation specialist for return to sports were eligible for inclusion in this study. At a minimum of six months postoperatively, we performed Y-balance testing per published protocols on the operative and nonoperative legs. Absolute measurements of Y-balance reach in the anterior (ANT), posteromedial (PM), and posterolateral (PL) directions were recorded, and a composite score was calculated from the average of all three values and normalized for limb length (anterior superior iliac spine to distal medial malleolus). The stance leg was considered the tested leg. Mean Y-balance scores between groups were compared with a two-tailed t-test, and statistical significance was set at p0.05. RESULTS: Testing was performed on 17 consecutive subjects who met inclusion criteria. The mean age was 23.18 years (range 15-45), and 10 were female (59%), while seven were male (41%). Mean time from surgery was 8.38 months (range 6-14). There were no significant limb length differences between limbs. Subjects demonstrated significantly lower scores (p=0.008) in the anterior direction (ANT) for the ACLR limb (60.48, SD=5.36) compared to the contralateral limb (63.25, SD=4.05). The PM, PL, and composite scores did not differ significantly between limbs, although there was a trend toward lower composite scores (p=0.088) in the ACLR limb (93.31, SD=4.57) compared to the contralateral limb (94.81, SD=6.127). CONCLUSIONS: ACLR patients who had been deemed ready for return to play demonstrated statistically significant lower Y-balance anterior reach scores in the ACLR limb as compared to the contralateral limb, and trended toward lower composite scores in the ACLR limb. The 2.77 cm anterior reach difference between limbs approached the 4 cm difference associated with increased initial injury risk in previously published studies. ACLR patients may continue to have lower extremity deficits in the injured limb even after returning to sports.