Hi everyone. Finally, I've solved the issue of the solution convergence, considering these conditions:

1) Increasing the size of meshing elements to reduce the solution time.

2) Imposing a "frictionless support" for the tibial face, because of the frictionless contact.

But, still there is a little difference between the stress values compared to the reference article. I mean, the acquired values for the stress distribution are about 10 times greater than the reported values from the paper.

Can anyone explain what could be the issue???