BackgroundVarious gait kinematic adaptations have been reported for patients with an anterior cruciate ligament deficient (ACLD) knee. However, to our knowledge, no study has compared their kinematics to their sex-matched controls for the entire gait cycle. Therefore, this retrospective study aims to identify differences in gait kinematics between ACLD patients and sex-matched controls.MethodsTwo databases were merged in this study, comparing knee gait kinematics of 44 injured males (ACLD-M) and 27 injured females (ACLD-F) with 32 healthy males (Control-M) and 37 healthy females (Control-F), respectively. Participants walked on a treadmill at a comfortable speed, and their movements were captured using the KneeKG® system.ResultsThe ACLD-M group showed a significantly decreased varus angle at several gait cycle sub-phases (from 17–32%, 57–73% and 86–97%; all p < 0.05) and an increased external tibial rotation from 67–86% of the gait cycle (p < 0.001) compared to the Control-M group. The ACLD-F group exhibited increased knee flexion from 1–53% (p < 0.001) and from 95–100% (p < 0.05) and increased valgus from 1–65% (p < 0.001) and from 94–100% (p < 0.05) of the gait cycle compared to Control-F group.ConclusionOur study reveals sex-specific adaptations following ACL rupture. Women exhibited more gait adaption in the sagittal and frontal planes during the stance phase while men demonstrated adaptations in frontal plane for sub-phases of stance and swing, and external tibial rotation during initial and mid-swing phases. These findings suggest that ACL injury kinematics and rehabilitation after injury should be sex-specific.