The Effect of Knee Flexion on Length Changes and Stress Distribution of Ligaments: A Displacement Controlled Finite Element Analysis

Abstract

The use of dynamic finite element analysis to investigate the biomechanical behavior of the knee joint is mainly based on movement of the joint. Challenges are associated with simulation of knee joint flexion-extension activity. This study investigated changes in the length and stress state of ligaments during lunge with a displacement controlled finite element analysis of the knee joint based on in vivo fluoroscopic kinematic data. The geometric center axis (GCA) was used to represent knee kinematics to quantify femoral motion relative to the tibia. Because the GCA was considered as a functional flexion axis, 2 degrees of freedom could be reduced. Published data on the in vivo fluoroscopic kinematic features of the GCA were used to establish the equations for degrees of freedom. Data for 4 degrees of freedom were obtained simultaneously at every 5° of knee flexion. Displacement and rotation were applied to the femur and tibia to produce relative displacement, and the elongation and stress state of the knee ligaments were computed. The predictions confirmed that lunge affected the biomechanical behavior of ligaments. Displacement controlled finite element analysis of knee flexion can be simulated on the basis of fluoroscopic kinematic data to achieve physiologic movement. [Orthopedics. 2021;44(1):e61–e67.]