What is the best artificial knee joint available for today?

The one your surgeon. The one your surgeon is comfortable putting in.
Surgeon's choice. There are several options, but as others have mentioned, most surgeons usually will have a preference... Asking your surgeon about their choice would be a great place to start. If i may, i also suggest you read "fits like a glove" @ http://drmarkgalland.Com/new-article-fits-like-a-glove/ for more information.