It's not totally true even for knees. Artificial replacement knees aren't as good as original knees.

I guess the point is that we might be able to simulate an artificial knee equivalent for neurons. It won’t be as good as a real knee, but it might still be useful.

I’d argue they’re better (in some ways), given that they’re “dead” material as opposed to functional tissue. Human knees don’t last nearly as long when the tissue is dead.

Lol. That's an interesting definition of "better".

If you're active, knee implants have to be replaced after 15-20 years, because they detach from the bone. Knee implants can harbor pockets of infections because they don't have an immune system. They are also more prone to dislocations.

They are objectively inferior to a healthy organic knee.

Yes, my comment was made a bit in jest. I think everyone will agree that after an arthroplasty, your quality of life is not as good as it was before.

But most of the reasons why artificial knees are not as good as the real deal have to do with the fact that they're made of inert (albeit fancy) materials. They don't have the ability to continually heal and do tissue remodelling, which is what real tissue does.

I feel very optimistic when I think about this: we're limited, but I think it's absolutely wonderful what we're able to do.

You should be able to relocate the instruction pointers in the stem cell's dna to patch in place the original knee with new living original knee.

Hope that reality isn't 50-years or more into the distant future.