Botte Aircast

Hi I had an ankle replacement just over four weeks ago. Overall recovery is going well. I had a cast on for two weeks and an aircast boot for the last two weeks. Two more weeks to go (hopefully) . But parts of my foot are really sore and I have a blister. Have anyone else encountered this? Not sure what I can do. 

I have a boot also following talo navicular surgery. 2 weeks in it so far and another 4 to go. Not had any soreness or blisters. I presume you have something on your foot inside the boot? I wear a thick sock in mine and its fine.