MR evaluation of the posteromedial corner of the knee: association of posterior horn medial meniscus tear with posterior oblique ligament and distal semi-membranosus tendon tear

Objective: To assess if posterior oblique ligament and distal semi-membranosus tendon tears are associated with posterior horn medial meniscus tears on MRI. Methods: From January 1, 2018 to December 31, 2019, 56 patients who met the inclusion criteria were enrolled in this study. Of the 56 patients, 43 patients who had a posterior horn of medial meniscus tear were included in the study group. A control group of 13 individuals was formed for comparison. Two radiologists reviewed the MR images and recorded the presence and grades of posterior oblique ligament and distal semi-membranosus tendon tears. We used the independent t-test and one-way ANOVA to compare the tear grades. Interobserver agreement was analyzed using a Cohen's kappa coefficient (kappa value) for categorical variables. Results: The mean grades for the posterior oblique ligament and distal semi-membranosus tendon tears were significantly higher in the study group (all, p < 0.001). Interobserver agreement between the two readers was substantial in assessing the grade of posterior oblique ligament tear (kappa = 0.653 +/- 0.087) and almost perfect in assessing the grade of distal semi-membranosus tendon tear (kappa = 0.876 +/- 0.060). Conclusion: Posterior oblique ligament and distal semi-membranosus tendon tears are significantly associated with posterior horn of medial meniscus tear and medial meniscus posterior root tears, and the peel-back mechanism could be related to this association. Advances in knowledge: Presenting this paper could adjust radiologist search patterns and potentially help orthopedists with management and pre-surgical planning for the posteromedial corner injury of the knee.