I've had a problem with my achilles tendons for ages which seemed to have been made worse by wearing walking boots which dug into the back of my ankles. After ditching them, I tried various kinds of shoes and trainers but they all still left me with sore and stiff ankles.
I was diagnosed with tendinopathy by the podiatrist I first saw and this was confirmed by another podiatrist after having ultrasound, though they found it to be more mechanical and not caused by the RA. I was told the tendon in my left foot, in particular, was a bit like a fraying rope. It was suggested I didn't waste my money on expensive orthotic insoles but that the best forms of treatment were to keep up with the specific exercises they give you for strengthening the achilles but also to try trail running shoes.
Well - I went to my local running shop the other day and ended up with a couple of pairs made by Brooks and Activ8 . They're fantastic. Very light, low enough at the back not to affect my achilles and they allow your feet to move naturally, without the restriction that ordinary shoes can cause. The Brooks, especially, are really comfortable and a little more supportive underfoot and ideal for every day wear. You can get a GTX version too, to keep the damp out, though these I've got do wick off the wet quite well. The Activ8s make your feet feel closer to the ground but the guy in the shop told me they might be better for the off road dog walking that I do as I can feel my way over the uneven areas.
All these years I've been led to believe that for off road walking, you needed a solid, stiff boot to protect the ankle. It would seem that this isn't always such a good idea as boots like that just hold your feet in one position and don't allow for enough natural flexibility. Can't believe for the first time in, I don't know how long, I'm walking without pain!