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The description of the human knee as four-bar linkage

Dathe H., Gezzi R., Fiedler Ch., Kubein-Meesenburg D., Nägerl H.

Acta of Bioengineering and Biomechanics

2016

Vol. 18, no. 4

107--115

Purpose: We investigate the dependence of the kinematics of the human knee on its anatomy. The idea of describing the kinematics of the knee in the sagittal plane using four-bar linkage is almost as old as kinematics as an independent discipline. We start with a comparison of known four-bar linkage constructions. We then focus on the model by H. Nägerl which is applicable under form closure. Methods: We use geometry and analysis as the mathematical methods. The relevant geometrical parameters of the knee will be determined on the basis of the dimensions of the four-bar linkage. This leads to a system of nonlinear equations. Results: The four-bar linkage will be calculated from the limits of the constructively accessible parameters by means of a quadratic approximation. Conclusions: By adapting these requirements to the dimensions of the human knee, it will be possible to obtain valuable indications for the design of an endoprosthesis which imitates the kinematics of the natural knee.

A finite element model for the wear analysis of polyethylene inserts in total knee joints

Bignardi C., Cavatorta M. P., Maggiora A., Calderale P. M.

International Journal of Applied Mechanics and Engineering

2001

Vol. 6, no 4

1109-1117

In the present work, a wear evaluation of the UHMWPE tibial insert of a total knee joint is attempted based on a simple wear model. A user subroutine has been written and integrated into a commercial finite element program to allow for a structural-kinematic model of the joint. The kinematic model simulates the relative angular velocity and linear movements between tibia and femur during walking. The input data consist of internal-external rotation and flexion-extension angle as taken from the literature. In the simulation, the femoral and tibial components are compressed vertically under gait loads, while at different orientations as determined by the kinematic model. A stress history of each element during the gait cycle is determined. The calculation of the product between the contact pressure and the node relative velocity, as given by the kinematic model, is then used for a qualitative determination of wear maps.