Deep medial collateral ligament plays a stabilising role under degenerative medial meniscus root tears

Abstract Purpose Several posterior medial meniscal root (PMMR) repair techniques have been developed to restore the load‐bearing function of the meniscus and reduce extrusion. The medial meniscotibial ligament (MMTL) has been shown to play a significant role in meniscal stability. This study evaluates the stabilising function of the MMTL by directly influencing the force exerted on the PMMR during weight‐bearing and valgus motion of the knee. Our aim is to investigate whether loss of MMTL integrity is a determining factor in PMMR subluxation. Methods Using a 3D model of the knee with parameters from experimental studies, compressive and valgus loading scenarios were simulated using the finite element method to analyse the mechanical response of different knee structures. To investigate the correlation between the integrity of the MMTL and the force acting on the PMMR, different degrees and types of injuries to both structures were modelled for comparison with the healthy joint, providing insights into their importance in preventing or correcting extrusion. Results During compressive loading, tears in the MMTL and PMMR result in a 5.8% and 30.9% increase in meniscal extrusion, respectively, while a combined injury results in a 43.9% increase, indicating that the MMTL provides a secondary constraint against extrusion. Moreover, the importance of the MMTL in restraining extrusion becomes more pronounced as the PMMR weakens, as is typical in degenerative tears. Finally, during valgus motion, the MMTL prevents separation of the meniscus from the tibial plateau and reduces strain/stress on the PMMR. Conclusion The integrity of the MMTL plays a crucial role in reducing meniscal extrusion and PMMR overload, particularly when the root is affected by degenerative tears. Therefore, surgical repair of the MMTL can improve meniscal function, potentially reducing the risk of osteoarthritis and should be considered as a better treatment strategy for PMMR tears. Level of Evidence Level III.