Background: The combined anterior tibial translation (ATT) and tibial internal rotation (TIR) is known as anterolateral rotational knee instability (ALRI). It is brought on by damage to the knee's anterolateral (AL) soft tissue structures and anterior cruciate ligament (ACL). Even after proper anatomic repair, it remains a common reason for ACL reconstruction (ACLR) failure. Objective:To assess the clinical and functional results of treating high-grade ALRI by combining arthroscopic ACL restoration with lateral extra-articular tenodesis (LEAT) performed using a modified Lemaire method. Patients and Methods:This study enrolled 30 cases with high-grade ALRI treated in the Department of Orthopedic Surgery at Menoufia University Hospital from November 2019 to February 2021. Results:Hard endpoint and delayed hard endpoint Lachman and Glide Pivot Shift (PS) were significantly increased postoperatively than presurgically; whereas, soft endpoint Lachman, Clunk and Gross Pivot Shift, Anterior drawer test (ADT) and McMurray test were significantly diminished postoperatively than presurgically (P<0.05). Lysholm and IKDC subjective scores increased considerably postoperatively than preoperatively; extension deficit and flexion range significantly decreased postoperatively (P<0.05). Conclusion: Laboratory investigations of the constraint offered by the lateral anatomical structures and the assessment of the decrease of rotational laxity have accumulated data in favor of a lateral extra-articular surgery to an intra-articular ACL restoration.