The Research On Biomechanical Change Of Knee Osteoarthritis Based On Finite Element Analysis Of The Tibiofemoral Joint

The knee is one of the most important and complex body joints.Because of the large amount of exercise in the daily life, the knee can bevulnerable to injury. The knee osteoarthritis (OA) is a kind of chronicosteoarthritis that is caused by the pathological changes of normal knee. Itmainly occurs in the aging population. The patients suffering the severeknee OA could lose the work ability and independent living skills. At thesame time, the various treatment costs bring huge economic burden to thefamily and society.At present, the pathogenesis of knee OA is not very clear. It isgenerally assumed by medical experts that meniscal and cartilagedegeneration is result of the long-term interaction between mechanics andbiological factors in the progression of knee OA. Therefore, the researchon biomechanical change of knee OA benefits to clarify the pathogenicprocess of mechanical factors.Based on the collected CT and MRI image datum of six normal kneesand six OA knees, total12three-dimensional (3D) geometry models ofnormal knees and OA knees were reconstructed in MIMICS software.Every model contained femur, tibia, fibula, meniscus, femur cartilage, tibiacartilage and collateral ligaments. The models were transferred intoHYPERMESH software for mesh generation. Each structure of the modelswas meshed with different element types. The comparisons between eachstructure of3D mesh models and the corresponding CT or MRI image datum were performed to guarantee the accuracy of the3D mesh models.Then, the3D mesh models were imported into ABAQUS software. At last,the simulation was done after the material properties setting, boundaryconditions and loading definition by ABAQUS. The maximum Misesstress on medial and lateral meniscus, the maximum Mises stress onmedial and lateral part of cartilage and contact area on medial and lateralpart of cartilage were obtained.According to the simulation results, the indexes of normal kneesincluding the ratio between maximum Mises stress on medial meniscusand the one on lateral meniscus, the ratio between maximum Mises stresson medial part and the one on lateral part of cartilage and the ratio betweencontact area on medial part and the one on lateral part of cartilage werecompared with the corresponding indexes of OA knees. It was shown thateach indicator of OA knee is substantially higher than that of normal knee.They demonstrated that the medial side of OA knee bears more loads thanthe normal state. It leads to serious wearing of the medial side in OA kneejoint. This coincides with the phenomenon that the thickness of medialmeniscus and medial part of cartilage from the observation of MRI andmedial clearance between femur and tibia from the observation of CT inOA knee are smaller than the normal state. The mechanics pathogenesis isclarified by the research.