Relationship between medial plica and medial femoral condyle-a three-dimensional dynamic finite element model

BackgroundMany researches reported that the pathologic medial plica impinges on the facing medial femoral condyle during knee motion and leads to erosive changes of the articular cartilage. The purpose of this study was to construct a simplified three-dimensional dynamic finite element human knee model to evaluate the dynamics behaviour between different types of medial plicae with the facing medial femoral condyles during knee motion.MethodsA three-dimensional dynamic finite element model composed of femur, tibia, covering cartilage and medial plica was developed. The kinematics of this simulation model was verified by previous findings during arthroscopic examination. The validated model was used to investigate and compare the magnitudes of the cyclic pressures acting on the cartilage of the medial femoral condyles by three different types of medial plicae with various Young's moduli.FindingsAll types of plicae remained in contact with the medial femoral condyles and shifted medially when the knees moved from extension to flexion. The contact pressures were positively correlated with the Young's moduli of the medial plicae. During the whole range of motion, the maximum contact pressures of all simulation scenarios occurred when the knees moved beyond 50° of flexion. When the Young's moduli of medial plicae were set greater than 60 MPa, all types of medial plicae would elicit contact pressures greater than 10 MPa on the medial femoral condyles.InterpretationThe close relationship and possible high contact pressure between fibrotic medial plica and medial femoral condyle during knee motion might be a cause of cartilage damage on the medial femoral condyle and warrants further investigation.