The biomechanical function of connective tissues in a knee joint is to stabilize the kinematics-kinetics of the joint by augmenting its stiffness and limiting excessive coupled motion. The connective tissues are characterized by an in vivo reference configuration (in situ strain) that would significantly contribute to the mechanical response of the knee joint. In this work, a novel iterative method for computing the in situ strain at reference configuration was presented. The framework used an in situ strain gradient approach (deformed reference configuration) and a detailed finite element (FE) model of the knee joint. The effect of the predicted initial configuration on the mechanical response of the joint was then investigated under joint axial compression, passive flexion, and coupled rotations (adduction and internal), and during the stance phase of gait. The inclusion of the reference configuration has a minimal effect on the knee joint mechanics under axial compression, passive flexion, and at two instances (0% and 50%) of the stance phase of gait. However, the presence of the ligaments in situ strains significantly increased the joint stiffness under passive adduction and internal rotations, as well as during the other simulated instances (25%, 75% and 100%) of the stance phase of gait. Also, these parameters substantially altered the local loading state of the ligaments and resulted in better agreement with the literature during joint flexion. Therefore, the proposed computational framework of ligament in situ strain will help to overcome the challenges in considering this crucial biological aspect during knee joint modeling. Besides, the current construct is advantageous for a better understanding of the mechanical behavior of knee ligaments under physiological and pathological states and provide relevant information in the design of reconstructive treatments and artificial grafts.

膝关节中结缔组织的生物力学功能是通过增加关节的刚度并限制过度的耦合运动来稳定关节的运动学。结缔组织的特征在于体内参考构型（原位应变），这将大大有助于膝关节的机械反应。在这项工作中，提出了一种新的迭代方法，用于计算参考构型下的原位应变。框架使用了原位应变梯度方法（变形的参考配置）和膝关节的详细有限元（FE）模型。然后在关节轴向压缩，被动屈曲和耦合旋转（内收和内转）下以及步态站立阶段研究了预测的初始构​​型对关节机械反应的影响。在轴向压缩，被动屈曲以及步态站立阶段的两种情况下（0％和50％），参考配置的包括对膝关节力学的影响最小。但是，韧带原位存在在被动内收和内旋下，以及在步态站立阶段的其他模拟情况下（25％，75％和100％），应力明显增加了关节的刚度。同样，这些参数大大改变了韧带的局部加载状态，并导致关节屈曲过程中与文献更好的吻合。因此，所提出的韧带原位应变的计算框架将有助于克服在膝关节建模过程中考虑这一关键生物学方面的挑战。此外，当前的构造有利于更好地理解生理和病理状态下的膝韧带的机械行为，并在重建治疗和人工移植物的设计中提供相关信息。