Posterior root of lateral meniscus: the detailed anatomic description on 3T MRI

Although there have been some attempts to reveal the anatomy of the posterior root of the lateral meniscus (PRLM) through cadaver studies, arthroscopy, or imaging, it has not yet been described fully.

To describe clearly the unique features of the PRLM, including its course, configuration, and size, using 3.0-T magnetic resonance imaging (MRI).

A total of 105 knee 3.0-T MR examinations of 103 patients with arthroscopically proven intact PRLM were reviewed retrospectively. Based on fat-saturated, proton-density-weighted (PDW) axial/coronal images and PDW sagittal images, the course, configuration, and attachment sites of the PRLM were evaluated.

The majority of PRLM (76.2%) had two attachment sites: the medial tubercle along the intertubercular crest, just posteromedial to the tibial attachment of the anterior cruciate ligament (ACL), and the posterior slope of the lateral tubercle. The remaining cases (23.8%) had a solitary insertion on the intertubercular area (17 cases), or the posterior slope of the lateral tubercle (eight cases). The PRLM of the intertubercular area appeared as a dark signal line parallel to the tibial plateau on the mid-sagittal image and dark signal foci traversing the intertubercular crest on contiguous coronal images.

The PRLM inserts mainly in the intertubercular area with a thin, long anterior extension to the point just posteromedial to the tibial attachment of the ACL. It is well delineated on PDW 3.0-T MRI as a dark signal line parallel to the tibial plateau on mid-sagittal images and dark signal foci traversing the intertubercular crest on contiguous coronal images.