I've (M57) had both knees replaced, left five years ago, right one year ago. Both were bone-on-bone. I go back in tomorrow to have my right knee worked-on again, because the joint is overly sloppy, causing some serious problems. Not sure yet exactly what they're be doing, it'll depend on what they find once they open me up. The left knee has been great, no problems with it. Obviously there's limitations to what an artificial knee can do, but biking hasn't been an issue. Even the problematic artificial right knee isn't too bothered by bike riding, it's walking that's the big problem. Different mechanics involved, I guess.
If your doctor says you need a new knee, go for it. The artificial knee itself isn't prone to problems (my own right knee nothwithstanding), it's the healing of the surrounding tissue that determines the success of the knee replacement. I'm guessing that you're relatively fit and active, which will help immensely with the rehab. Rehab ain't easy, but as long as you stick with it, you'll come out the other side in pretty good shape, knee-wise. The pain involved in rehab isn't the same sort of pain you're currently experiencing...it's "good" pain, if that makes sense, pain from working hard rather than the sick and grinding pain from inflammation and irritation.
My first knee was cemented into place. You can see the layer of cement on X-rays. As I understand it, when they say that an artificial joint has about a 20- to 25-year lifespan, it's usually the cement that eventually fails, rather than the joint itself. The teflon puck in the middle can wear out, too, but that's (relatively) easy to replace. That's what they're probably doing to my knee tomorrow, replacing the teflon puck with one that's about 4mm thicker, to tighten the joint up so there's not so much slop.
My right knee (again, done a year ago) is a press-fit into the bone. They literally hammer it into place, and the barbed titanium stub is held in place for the long-term by the bone that grows into the ridges of the stub. This is supposed to be far more permanent in the long-term than cement. There's more pain in the short-term, because of the violence involved (the doctor said it's not pleasant to watch being done), but the end result is much more permanent. Also, these new joints are shaped in such a way that the patella can be left as-is, instead of having the back milled flat and a thin teflon puck attached, like with my previous knee.
All in all, my experience with knee replacement has been pretty positive. The last eight months since I started having problems with the right knee have been admittedly discouraging, but overall I'm not regretting it. Like I said, bike riding hasn't been a problem with either knee. Obviously, I'm not going at it really hard in high gears, but I average about 18-20mph without any issues, including some pretty steep ascents. I think it's because the problem with the right knee is that it's very loose and sloppy, but while riding it's almost constantly compressed so that the sloppiness doesn't come into play.
Again, rehab is going to be what determines success, but you have to plan on it taking about a year before you're anything like 100%. You'll be amazed at how much you improve in the first 6-8 weeks...after that, the rate of improvement levels off, but assuming everything else goes well, you'll see gradual but constant improvement. My doctor said that, in general, non-rehab problems arise only about 15% of the time, and are generally straightforward to remedy. My right knee is in that 15%, I guess.
Hope this helps.