The human knee implant is computationally modelled in the mixed lubrication regime in order to investigate the tribological performance of the implant. This model includes the complex geometry of the implant components, unlike elliptical contact models that approximate this geometry.
Film thickness and pressure results are presented for a range of gait cycles in order to determine the lubrication regime present within the implant during its operation. It was found that it was possible for the lubrication regime to span between elastohydrodynamic, mixed and boundary lubrication depending on the operating conditions of the implant. It was observed that the tribological conditions present in one condyle were not necessarily representative of the other.
Multiple points of contact were found within the same condyle, which cannot be computed by elliptical contact solvers. The effect of the complex geometry was further apparent when the alignment of the geometry was shifted slightly, resulting in significantly different results. This model can balance forces in all directions, instead of only the normal loads, as often done in elliptical contact models. The computational intensity of simulating the complex geometry of the knee implant is compared with an elliptical contact model and the limitations of elliptical contact models are discussed.
This work is an initial step towards understanding the role of the complex geometry in the tribological characteristics of the human knee implant when operating in physiological conditions.