Posterior lateral meniscal overhang is associated with ACL tears: A retrospective case-control study

There have been several described imaging findings that correlate with anterior cruciate ligament (ACL) injuries. The investigators in this study observed a higher frequency of posterior translation of the lateral meniscus beyond the posterior border of the tibial plateau in patients with ACL tears. The purpose of this study was to assess the frequency and degree of posterior lateral meniscal overhang (LMO) of the lateral meniscus in patients with ACL tears compared to uninjured controls.

Magnetic resonance imaging (MRI) was analyzed in 117 knees with ACL tears and compared to a control group of 89 knees without injury. Lateral meniscus diameter, LMO, knee flexion angle, and lateral tibial plateau diameter were measured and compared between the two groups. Exclusion criteria included displaced and macerated lateral meniscus tears, multi-ligamentous knee injuries, and periarticular fractures. Difference in mean lateral meniscal overhang between ACL injured and control groups was tested using a paired T-test (alpha = 0.01). Assumptions for normality and variance were tested prior to analysis.

In patients with ACL tears, average LMO was significantly greater compared to the control group (0.95 mm vs. 0.08 mm; p < 0.001). Additionally, measurable LMO was found in 42.7 % of patients with ACL tears compared to 4.5 % uninjured knees (p < 0.001).

Patients with ACL injury show higher incidence of LMO compared to uninjured controls. Future studies are necessary to better understand its clinical significance.