Computer Simulation of the Knee Joint

Total knee arthroplasty (TKA) is an indispensable surgery for end-stage knee osteoarthritis (OA), but approximately 20% of patients in the patient-reported outcome measures have postoperative dissatisfaction. However, the cause of residual knee joint pain and instability is often not identifiable by clinical or imaging findings. The development of new implant designs [1] and surgical techniques [2–4] will require long-term observations to confirm the efficacy. Therefore, simulation analyses can be used to elucidate these issues. Currently, simulators using cadaver knees representing the Oxford Knee rig are established methods to analyze the knee joint biomechanics. In the setup, a cadaver knee with TKA is fixed to the simulator that mimics the lower limb, and the knee motion such as squatting or walking is performed to investigate knee kinematics and kinetics. One problem in using fresh-frozen cadaver knees is that the rigidity is lower than that of in vivo knees, and deterioration may occur during repeated testing. In Japan, formalin-fixed, rigid cadaver knees are readily available, while the facilities that use fresh-frozen, flexible cadaver knees are limited. Thus, a computer simulation analysis is developed as an alternative to cadaver knee biomechanics analysis, such as the finite element method (FEM) [5, 6] and musculoskeletal models [7, 8].