Abstract
PURPOSE: To compare biomechanical evidence on joint compression forces and rotational stability between isolated lateral meniscus posterior root (LMPR) tears and those with concurrent meniscofemoral ligament (MFL) injuries, with a secondary focus on assessing rotational stability in ACL-deficient and ACL-reconstructed knees. METHODS: A comprehensive literature review was conducted following the 2020 PRISMA guidelines, using the Scopus, PubMed, and Embase databases from their inception through 7 October 2024. This review included biomechanical studies on healthy animal or human cadaveric knees that assessed lateral compartment contact area and peak pressure following isolated LMPR and MFL injuries, as well as kinematic outcomes in anterior cruciate ligament (ACL) deficient knees. The methodological quality of the studies was assessed using the Quality Appraisal for Cadaveric Studies (QUACS) scale. RESULTS: Twelve studies involving 116 knees-86 human cadaveric and 30 porcine models-assessed tibiofemoral contact mechanics (contact area and pressure) and kinematic data. Both isolated LMPR tear and the combination of LMPR and MFL injuries significantly increased mean contact pressure in the lateral compartment compared to the intact state (p = 0.004 and <0.001, respectively). However, isolated LMPR tear did not significantly increase peak pressure in the lateral compartment (p = 0.55), whereas the combination with MFL injury caused a substantial rise (<0.001). LMPR repair restored both contact and peak pressures to levels that were not significantly different from those observed in the intact state (p = 0.86 and <0.28, respectively). Additionally, the combination of LMPR tear, MFL injury and ACL sectioning further increased anterior tibial translation (ATT) and internal tibial rotation (IR) during a simulated pivot shift test compared to isolated LMPR tear (<0.001). Although LMPR repair reduced rotational instability, it did not significantly restore ATT (p = 0.63) and IR (p = 0.923) during simulated pivot shifts in ACL-reconstructed knees. CONCLUSIONS: A combined injury to the LMPR and MFL significantly increases mean and peak contact pressures in the lateral compartment compared to isolated LMPR tear and intact states, with LMPR repair restoring contact pressure to near-normal levels. However, in knees with ACL deficiency or reconstruction, LMPR tear with MFL injury significantly increases IR during pivot shift testing, with LMPR repair unable to restore rotational stability to intact-state levels. LEVEL OF EVIDENCE: Level IV, systematic review of biomechanical studies.