Numerical Analysis Of Mechanical Properties Of Knee Joint In Gait And Mass Transfer Experimental Study On Articular Cartilage

Knee joint is one of the most important movable joints in the human body,whose health can affect the quality of life of the people.But the structure and mechanical environment of the knee joint are so complex that the incidence of knee-related diseases is always high,so carrying out research on the mechanical biological properties and functions of the knee joint is in extremely need.In this paper,kinematics and kinetic biomechanical properties of knee joint are studied by using dynamic simulation software and Finite Element method.First of all,using the dynamic human body simulation software LifeMOD to establish the multi-rigid body model of the normal adult male lower extremity,then setting the marker towing point and importing the motion track coordinates of the human joint acquired by the three-dimensional image,finally finishing the training of the joint movement agent through the forward and reverse movement simulation.After completing the gait simulation of multi-body model of human body,the effect of walking speed on mechanical properties such as force and angle of knee joint are investigated.The simulation results show that the joint force and angle show a certain periodicity at different paces,and as the pace increases,the joint angle changes faster and the joint force increases.At the same time,it is found that flexion movement of knee joint is the most important compared with other directions,while the horizontal plane is the main bearing area.The results can be verified that kinetic simulation of LifeMOD is in line with the dynamics of the human knee.Secondly,the Finite Element analysis of knee cartilage is performed on the base of kinetic results.According to the anatomy of the human knee joint,a complete geometric model is created through softwares such as Mimics,Geomagic,and Proe to meet the mutual relationship among the organizations,which realizes the transformation from human body data scanned by medical entity to mechanical analysis model.Then based on the complete geometric model of the knee joint,the finite element model is finally completed by assembling,dividing the mesh,assigning unit properties,material properties and constraints.This article innovatively combines dynamics simulation software and finite element software to explore the influence of walking speed on the contact stress of cartilage from the aspects of sports biomechanics and solid biomechanics.The simulation shows that when the walking speed is changed,the angle of the knee joint in the sagittal plane changes greatly.The joint force is large and corresponds to the actual movement of the knee joint.As the pace increases,the period of change of joint angle is accelerated,the size of joint force is periodic,and the joint force can also increase in size.The model with cartilage defect is further established to analysis the effect of defect area and the load on cartilage defect.It is found that the stress of knee joint cartilage is proportional to the size of the force,and the upward trend in cartilage defect is more obvious.Thirdly,by summarizing the physiological and mechanical characteristics of articular cartilage,a dual-frequency bioreactor is designed to study the mass transfer characteristics of human cartilage by simulating the various mechanical loading environments of the human body.Which combines with optical microscope,mechanical loading test machine and medical-related tracer to design mechanical experiments about cartilage mass transfer.In this paper,the effect of loading time,loading frequency,amount of compression and dye on mass transfer of cartilage are studied.The experimental results show that the mass transfer of the dye in the middle part of the sample at the same loading condition is faster than that in the middle part of the same sample;At the same loading time,the increase of loading frequency and compression can speed up the process of mass transfer of cartilage;while at the same loading time and loading frequency,the amount of compression can accelerate the cartilage mass transfer process;in the same amount of compression loading frequency,mass transfer effect is more obvious with the loading time getting longer;In addition,loading can speed up the rate of mass transfer in comparison with the control group.Futher more,the mass transfer process does not have a positive correlation with the loading frequency under the same compression and loading time.In the mass transfer process,the staining begins mainly from the cartilage surface,but the dye slightly up-infiltrates from the subchondral bone.In summary,the structure and function of the knee joints are adapted to the mechanical stimulation.When the mechanical loading conditions such as external load / compression depth / pace / time are changed,the stress in each tissue in the joint can change,When the load / compression depth / pace / time increases,the joint force / joint torque can also increase positively,and the process of the cartilage mass transfer can also be significantly improved.These rules also apply to the cartilage defect model.