Lateral meniscus posterior root tears in the anterior cruciate ligament–injured knee: Current concepts

Lateral meniscus posterior root tears (LMPRTs) compromise load transmission and secondary stability in the anterior cruciate ligament (ACL)-injured knee and may be missed on magnetic resonance imaging (MRI). This narrative current-concepts review addresses incidence, risk factors, biomechanics, diagnosis, classification, treatment, and outcomes, while distinguishing root tears from lateral meniscal oblique radial tears (LMORTs). Primary ACL reconstruction (ACLR) cohorts report LMPRT frequencies of 7.1%, 10.0%, and 12.2%; a mixed primary/revision cohort reports 6.6% and selected revision cohorts report 20.5% and 40.7%. These study-specific estimates differ in lesion definition and ascertainment. Contact injury, concomitant medial meniscal pathology, and increased lateral posterior tibial slope are recurring associations. Individual MRI signs have limited sensitivity; combined assessment and arthroscopic inspection and probing support diagnosis. LaPrade et al. describe root-tear morphology, Forkel and Petersen additionally consider meniscofemoral ligament integrity, and LMORT typing describes posterior-horn oblique radial tears. The systems overlap for near-root lesions and are descriptive frameworks rather than validated treatment algorithms. Selected stable lesions may be observed; repairable unstable lesions are generally treated with footprint fixation or side-to-side repair, according to anatomy and tissue quality. Repair with ACLRn is associated with improved patient-reported outcomes and high complete-or-partial healing proportions in selected series. Clinical improvement in ACL graft survivorship has not been demonstrated. Heterogeneous definitions, predominantly lower-level evidence, variable rehabilitation, and limited long-term comparative data, constrain conclusions about cartilage preservation and optimal treatment.