Is it definitely AT if it is I had it for 3 years and the thing that got rid of it was heel inserts.
I went to the docs and then got referred to a specialist that moulded my feet and produced an insole.
Within a week it had gone.
Funny enough but not funny its back and I no longer have the insoles,perhaps I need to adhere to my own advice.
Don't have cortisone injections they are short term fixes and when they wear off it comes back worse in my experience.