Anterior cruciate ligament reconstruction with lateral plasty restores anterior-posterior laxity in the case of concurrent partial medial meniscectomy.

To evaluate the in vivo knee laxity in the presence of a partial medial meniscectomy before and after a single-bundle ACL reconstruction with a lateral plasty (SBLP) and to compare it with the knee laxity after a single-bundle ACL reconstruction (SB). One-hundred and one patients with ACL tear were enrolled in the study and grouped according to the surgical technique and the meniscus treatment: regarding the SBLP technique (n = 55), 31 patients underwent isolated ACL reconstruction (“SBLP Isolated ACL Group”), while 24 patients underwent combined ACL reconstruction and partial medial meniscectomy (“SBLP ACL + MM Group”); regarding the SB technique (n = 46), 33 patients underwent isolated ACL reconstruction (“SB Isolated ACL Group”), while 13 patients underwent combined ACL reconstruction and partial medial meniscectomy (“SB ACL + MM Group”). Anterior–posterior clinical laxity at 30° (AP30) and 90° (AP90) of knee flexion was quantified before and after surgery through a surgical navigation system dedicated to kinematic assessment. In the ACL-deficient status, the antero-posterior laxity was significantly higher in the presence of a combined MM in both the AP30 and the AP90, with no differences between the two surgical techniques. After the ACL reconstruction, both AP30 and AP90 translations decreased significantly (p < 0.0001) compared to the ACL-deficient status. No differences were found for AP30 and AP90 between SBLP Isolated ACL and SBLP + MM groups, while a significantly higher AP90 translation was found for the SB + MM group compared to the SB Isolated ACL group. Moreover, the AP90 translation in the SB ACL + MM group was significantly higher than the one of the other three groups, i.e., SBLP ACL + MM, SB, and SBLP Isolated ACL group. The ACL reconstruction with lateral plasty reduced the AP knee laxity caused by the medial meniscectomy in the context of an ACL surgery. Level II.