I am not sure of how many, but for me, I started with issues on my left foot/ankle/leg. About 4 months after everything started on the left side, the right side started with the exact same symptoms, just a little bit more mild.
I am 6 weeks post op from surgery on the left PTT, and the right one has held up pretty well, with me relying on it, however, its starting to give, so I am a little concerned---BUt we knew this was a possibility from the start---the Ortho said he was hoping that surgery on the left, would maybe "help" the right one from going downhill.
But I will say----my severe pain would hit when i was on my feet for awhile---I am fairly active and always "on the go"---and on the days where I had cleaned house, or been on my feet baking cakes ( a side job/hobby)---I would be in tears, and barely able to function, and would have to sit down for several hours to recover-----I would catch myself "rolling" my ankles on each foot to walk.
So I guess my point, is that, my right is probably not in the best of shape---BUT I don't think its nearly ready for surgery. At least I HOPE not----I have been bored out of my mind these last few weeks---and I still have 3 weeks to go, before I go back to work!!
Best wishes to you---I really hope your situation improves