Well for me this was quite a difficult bridge to cross, which I haven't yet. I have had bad hip pain for 5 years, but finally went to an ortho for it in July 2010. That is when I was told that I was bone on bone.
At this point I am still have a baby (6 months old) that is nursing, so I know I am not going to do anything. I swear after I was diagnosed, I felt the pain even more. Fast forward to today, I have copped with PT and swimming in the pool, but not able to walk much. THis is really hard with the kiddos. I am a very active person that cannot do anything with her family.
The final straw was a work issue. It was a gorgeous sunny day and I walked a block to the post office to send off a letter. After that I went to get a company car, but could not find it. I looked around to city blocks, and could not find it. I had to give up, because of the pain in my hip. It was sunny, I love any excuse to walk outside when it is sunny. I realised at that moment, I need to get surgery.
I am still nursing my baby, who is 16 months old, but I do not care, I need to do this for them. I decided that I wanted the surgery on May 11, the day after my sons birthday. I called the surgeon, and he had the day available. I asked my husband and he was good with that time. I asked my boss and he was good with that date.
I think that you know when, you just need to trust yourself. Hope this helps, but again I am still on the bridge, I can chicken out at any point.