Anatomic reconstructions of anterior cruciate ligament (ACL) with double bundle gracilis and semitendonosus tendons graft, reproducing AM and PL bundles, have been introduced to offer a better biomechanical outcome, especially during rotatory loads. On the other hand, many methods of tenodesing the lateral aspect of the tibia to the femur to reduce internal rotation (IR) of the tibia and minimize anterior translation of the tibia relative to the femur as a backup for intra-articular reconstruction, have been also suggested. The goal of this study is to evaluate the effect, on the IR of the tibia, of a lateral reconstruction in addition to a standard single bundle ACL reconstruction as compared with an anatomic double bundle ACL reconstruction. Computer assisted ACL reconstruction has been used because it could be very effective in evaluating the global kinematic performance of the reconstructed knee. We selected 20 consecutive ACL reconstruction procedures to be performed in males in our hospital. Patients were alternately assigned to one of the two groups--group A: standard single bundle ACL reconstruction with doubled gracilis and semitendinosus tendons graft with an arthroscopically assisted two incisions technique and a lateral extraarticular reconstruction; group B: double bundle ACL reconstruction with doubled gracilis and semitendinosus tendons graft with an arthroscopically assisted two incisions technique. In all ACL reconstruction procedures navigation process was performed. Both surgical techniques reduced significantly AP displacement, IR and external rotation (ER) of the tibia respect to pre-operative ACL deficient condition (p<0.05). Comparing the group A after the single bundle reconstruction and the group B after the AM bundle fixation, non differences were found in AP displacement, IR and ER of the tibia (p=0.75, p=0.07 and p=0.07 respectively; power: 0.94). Comparing the group A after the addition of the lateral tenodesis and group B after the PL bundle fixation (AM+PL) no differences in AP tibial displacement and in ER of tibia were found (p=0.9 and 0.15, respectively; power: 0.99); however a significant reduction in IR of the tibia was found in group A after the addition of the lateral tenodesis respect to the group B after the addition of the PL bundle (p=0.0001; power: 0.26). On the basis of our study, the addition of a lateral extraarticular reconstruction to a standard single bundle ACL reconstruction with hamstrings tendons graft in an "in vivo" reconstruction, is more effective in reducing the IR of the tibia at 30 degrees of knee flexion, as compared with a standard single bundle ACL reconstruction and with an anatomic double bundle reconstruction is confirmed.