Objective To investigate the effects of rotation stability after anterior cruciate ligament reconstruction (ACLR) on subjective outcomes,sport performance,psychological readiness,and return to sport. Methods The patients who underwent ACLR in the Sports Hospital,National Institute of Sports Medicine,General Administration of Sport of China from January 2015 to January 2021 were followed up during the period from November 2022 to December 2023.The patients were grouped according to the results of the pivot shift test (PST) of the affected knee at the last follow-up visit.A total of 66 patients who participated in the follow-up and met the inclusion and exclusion criteria were finally enrolled in this study,including 32 patients showing a negative PST result (stable group) and 34 patients showing a positive PST result (unstable group).The basic information,subjective function score,and return-to-sport performance were compared between the two groups. Results In terms of sport performance,the two groups showed differences in the limb symmetry index in single-leg hops,triple hops,and crossover hops (P=0.028,P=0.024,and P=0.044,respectively).The anterior cruciate ligament-return to sport after injury scale score was higher in the stable group than in the unstable group [(70.44±22.82) scores vs. (53.44±21.74) scores,P=0.003].The mean of KT-2000 test results in the stable group was lower than that in the unstable group [(0.53±1.02) mm vs. (2.06±2.31) mm,P=0.001].The Lysholm score,international knee documentation committee score,knee injury and osteoarthritis outcome score,Tegner score,and Marx score did not have significance between the two groups (all P>0.05).The return-to-sport rate was 43.8% (including 14.3% reaching safe return criteria,which accounted for 6.3% in all the patients) in the stable group and 35.3% (including 8.3% reaching safe return criteria,which accounted for 2.9% in all the patients) in the unstable group.There was no difference in the 60°/s isokinetic muscle strength,maximal muscle strength ratio of the affected extensor-flexor muscles,or Y-balance test result between the two groups (all P>0.05). Conclusions Knee joint rotational instability after ACLR results in poor performance in single-leg hops,triple hops,and crossover hops,low psychological readiness,and anterior-posterior knee laxity.In short- to medium-term follow-up for ACLR,the return-to-sport rate remained low regardless of knee joint rotational stability,with the majority of patients failing to meet safe return criteria.