I have just joined the group after, like many people whose posts I have read so far, suffering from arthritis in my lower thumb joints in both hands for a few years. I have used small hand-tools all my working life, and in my hobby at home, now I avoid using a pair of pliers or wire cutters for any period of time...
There is one thing which I have found really helpful which I wanted to share - and that's wearing gloves in bed. Sounds strange I know, but I have found the extra heat in the joints over the last couple of months has helped enormously. I did leave them off for a week or so, the previous pain returned, and when I started wearing them again it eased again. Not very scientific, but it certainly works for me. 40gm Thinsulate gloves - a pound a pair on the local market. Well worth trying if you have the same problem.