Associated Medial Meniscal Injury with ACL Reconstruction Results in Poorer Strength and Jump Tests Outcomes: A 6-Month Analysis of 504 Patients from the MERIScience Cohort

<b>Background/Objectives</b>: After anterior cruciate ligament reconstruction (ACLR), a 6-month composite test is recommended during rehabilitation before the return to sport, and the influence of a meniscal tear is not known. The hypothesis was that the location and treatment of meniscus injuries could influence the results of the composite test. <b>Methods</b>: A retrospective single-center study was carried out of prospectively collected data involving 504 patients who performed a composite test 6 months after ACLR. Isolated ACLR was compared to ACLR with medial meniscus injuries (MM), lateral meniscus injuries (LM), and bimeniscal injuries (BM) using a composite test including a single-leg squat (SLS), a single-leg landing (SLL), a single hop for distance (SHD), a triple hop for distance (THD) and a side-hop test (Side-HT), isokinetic strength tests, and an assessment of the anterior cruciate ligament-return to sport after injury (ACL-RSI). <b>Results</b>: Compared with isolated ACLR, MM injury was associated with a quadricipital deficit at a velocity of 240°/s (14% ± 14% vs. 18% ± 18%, <i>p</i> = 0.02), hamstring deficit at 30°/s (14% ± 18% vs. 18% ± 18%, <i>p</i> = 0.02) and an increase in the hamstring/quadricipital ratio at 240°/s (68% ± 27% vs. 80% ± 67% <i>p</i> = 0.02). Furthermore, ACLR + MM or ML injuries in the operated knee generated an increase in the dynamic valgus frequency detected by the SLS, respectively (40% ± 49% vs. 51% ± 50%, <i>p</i> = 0. 05) and (40% ± 49% vs. 54% ± 50%, <i>p</i> = 0.02). Meniscal repair and meniscectomies showed no differences. <b>Conclusions</b>: These results show that meniscal injuries lead to muscle imbalance for MM injuries and impaired neuromuscular control for MM and LM injuries and suggest that meniscal repairs should be done. Moreover, rehabilitation must be adapted to meniscus injuries.