Hi Tina
Sorry, I don't really know Daniel's history with RA but can I suggest that you get someone to check his feet? Often the metatarsal heads on the soles of the feet, the area behind the toes, can become inflamed and sore. The continual use of the feet means that the only rest they get is when we are in bed. The metatarsal heads can give a burning sensation.
I don't know whether Daniel is obliging but if you can get him to let you have a look there may be some evidence of hard skin over the heads if this is the problem, it's nature's way of protecting the damaged joint but the hard skin in itself can cause some problems. Either way if you can feel along the base of the foot and see whether there are any raised bumps it may give you some indication. The sensation you get is one of walking on pebbles on a beach.
There are of course other things it could be and fingers crossed it is one of those BUT it is common to find RA in the metatarsal heads and early diagnosis is crucial to 'save' those joints by referral to a podiatrist.
Perhaps I haven't explained very clearly, it's been a long day! Come back to me if you wish and I'll try and help
Lyn x