Objective This study aims to investigate the MRI appearance and diagnostic value of the posterior horn of the lateral meniscus (PHLM) tear of the knee ligament attachment zone.

Methods From December 2012 to June 2018, 35 patients with anterior cruciate ligament (ACL) injury combined with PHLM tear in the knee ligament attachment zone were selected as the observation group. Thirty patients with ACL injury but without PHLM tears were collected as the control group A. Another 30 healthy people who received routine physical examination were selected as the control group B. All subjects received knee MRI examination. The MRI performance of all subjects in the three groups was observed. χ² test, one-way ANOVA, and t-test were used to calculate the incidence of knee MRI signs, the damage of the structure around the knee joint, and the number and length of the linear high-signal images of the knee joint. The receiver operating characteristic curve was used to analyze the effectiveness of differential diagnosis of true and false tear in PHLM.

Results Patients in the observation group showed significant linear hyperintense on the MRI sagittal plane and cross-sectional images. The sagittal plane was continuously detected (5.75±1.38) layers (called "continuous line sign"), extending from the inside to the outside (15.06 ± 5.02) mm (called "zipper sign"). The number of layers on the sagittal plane and the length of the transverse section in the observation group were higher than those in the control groups A and B ( F =43.231, 36.113, both P < 0.05). Combined with "continuous line sign" and "zipper sign" as the positive criteria, the sensitivity was 85.71%, the specificity was 95%, and the accuracy was 91.58%.

Conclusion The PHLM tear in the knee ligament attachment zone had obvious signs on MRI, supplemented by "continuous line sign" and "zipper sign" for differential diagnosis, which could significantly improve the diagnostic effect.