Sliding-Rolling Ratio during Deep Squat with Regard to Different Knee Prostheses

The sliding-rolling ratio between the femoral and tibial condyles throughout the active functional arc of the knee (20-120 degrees of flexion angle) is currently unknown. Since wear is the most determining lifetime factor of the current total knee replacements, the presence of sliding-rolling cannot be neglected. The reason lies in the fact that this phenomenon causes different material abrasion compared to pure sliding or rolling alone. Only a limited amount of studies have dealt with this question related to the condyles of the knee prostheses, most of them by means of experimental tests and only in the segment where the motion begins (0 to 20-30 degrees). The primary aim of this paper is to investigate how the sliding-rolling ratio changes between the condyles of five different knee prostheses in the functional arc of the knee (20-120 degrees) as a function of flexion angle. For the analysis, five prosthesis models with identical boundary conditions have been constituted and numerical simulations were carried out using the MSC.ADAMS program system. Beside the sliding-rolling ratio, the normal and friction force between the connecting surfaces has also been calculated as a function of flexion angle.