My advice would be to walk as far as you can without the pain you described. If you can do 2 miles that is great. If even that is very difficult, I would try another form of exercise. Mine is water aerobics. I can jog very vigorously for two hours without any pain which I could never do on land. When I broke a hip years ago, walking in the water was what I did in PT. You endure so much pain when walking - and do so much to avoid it - it is obvious that wallking now is not the pleasure it once was and sadly may never be again. I would never attempt the 6-7 mile hikes I once took up and down the mountain trails in Oregon - that is why I turned to the water.