Steve, I feel like I was pretty much where you are now a few of years ago. Intermittent pain, nothing serious showing up on X-rays, no noticeable reduction in ROM, and not much change for several years. Then (pretty suddenly, it seemed), I started having a lot of pain in my right thigh, which I thought was muscle strain, only it never went away. It didn't really stop me from doing anything, but the pain was constant at that point. I lived with that for about 6 months before I went to the orthopedist, who was a sports medicine doctor, not a hip guy. He saw nothing on X-rays, prescribed PT for 6 weeks which did nothing, except make it obvious that my ROM was not good, then sent me for an MRI and referred me to a hip specialist in the same practice. OA showed up on the MRI. The hip guy said he could give me a hip replacement when the pain got bad enough. I did not want that, so I waited about another 9 months before I found out about Dr. Gross and went to see him. He told me that the X-rays showed I was bone on bone in both hips, only I had hardly any pain on the left side. I had my right hip resurfaced last April, and it's doing great, but now my left one has started hurting!
As others have said, we are all different, and we all have a different threshold for what we can tolerate. I'll be very interested to hear the results of your visit with Dr. Su next week.