Well, this is good info. I have read up on the glucosamine subject slightly and it seems like it depends on who you talk to as to the effectiveness. My wife is all over it, though, so I have a feeling I'll be trying it.
My doctor (after x-rays and physically evaluating the joint itself) suggested Ibuprofen (or Celebrex) as a first step followed by cortisone injections. Knee replacement was brought up but only as a distant future solution. My knee joint is "stable" and doesn't appear to have any issues other than the cartilage degeneration.
I think the sobering reality is that I'm getting olde.