Kinematics in Total Knee Arthroplasty

Kang, Seung Baik

Abstract

In the current age of technological advances, reproducing the knee kinematics for minimizing wear and increasing the range of motion, together with obtaining proper alignment and stability, have become the major goals of total joint replacement. The kinetics of total knee arthroplasty (TKA) have a complex influence on its performance, and differing abnormal patterns have been shown after TKA by using gait analysis, fluoroscopy and radiostereometry. In the sagittal plane, it is now understood that the femoral condyles roll and glide simultaneously on the tibial plateau during flexion. The kinematics of the knee and the shape of the condyles and the tibial plateau are closely interrelated with the functions of the cruciate ligaments. The kinematics result from the combined actions of the surface geometry of the joint and the soft tissues attached to it. To a variable extent in the mid-range, these factors cause tibial internal rotation to occur with flexion around a medial axis. From 120_ to full flexion, both condyles roll back onto the posterior horn so that the tibio-femoral joint subluxes. In TKA, it has been demonstrated that substituting a cam-and-post mechanism for the PCL (posterior cruciate ligament) shows consistent posterior femoral rollback during flexion. Restoration of the posterior condylar offset is important since it allows a greater degree of flexion before impingement occurs.