Hey I know this is a late response but I am new here. I had left THR last week due to AVN and collapse. I was away for many months and started to have the awful pain in December 2017 — and walked on it and walked on it — probably for 200 miles and 7 months until my diagnosis on June 25 when I returned to the States...and the femoral head had collapsed. I was on the couch/crutches for 8 weeks waiting for surgery. Now I am on day 7 post-surgery. It has been really frustrating for me not to know the reason for the AVN. I am in the small percentage of folks who have unknown etiology. Good times. I hope your joint replacements have been successful. Left THR August 21, 2018 due to AVN.