The effect of healing in the medial collateral ligament of human knee joint: A three-dimensional finite element analysis

The medial collateral ligament (MCL) is one of the main ligaments that provide knee joint with major restraints against valgus, internal, and external torque loads. The MCL injury most frequently occurs near its femoral attachment but can be healed spontaneously. Hence, the usual clinical treatment for MCL injury is conservative therapy with early controlled rehabilitation motion. However, the effect of the variations in the healing conditions of the MCL portion (i.e. near the femoral insertion) is still unclear. In this study, finite element tibiofemoral joint models with three different MCL healing conditions were analyzed under six kinds of joint loads, such as 10 and 20 N·m valgus tibial torques, 5 and 10 N·m internal tibial torques, and 5 and 10 N·m external tibial torques. The three healing conditions corresponded to the early, medium, and final (i.e. healthy) stages of the healing period, respectively. It was found that different MCL healing conditions greatly affected the main joint kinematics under valgus tibial torques, but neither the reaction force nor stress results of the MCL. The peak strain values in the MCL healing portion changed greatly under all the six loads. Moreover, all the joint kinematics, strain results, and reaction force of the MCL at the medium stage were similar to those in the healthy joint, that is, at the final healing stage. These imply that the partially healed MCL might be enough for providing the restraints for knee joints and would not lead to some high strains occurring in the MCL.