Very sorry to hear of your pain.
I have some arthritis and RSI in most of my knuckles and a little in both my wrists, which is one reason why I have switched from guitar to ukulele actually for the easier fretting.
But I was originally a bass player. I made the switch to upright bass. Strangely, the increased scale actually helped in my instance because I no longer needed to squeezed swollen and painful joints into a small fret space and no longer had the need to play quickly or use so many fingers.
Maybe switching to a longer scale bass or actually being realistic about the basslines you play might help? I now find that by playing less I can be more expressive. It wasn't easy but certainly helped me.
A drummer friend of mine also has arthritis and carpal tunnel problems, and he has had to go through changing a lot of his technique and repertoire to allow him to still play. Trouble is, it was that or nothing so he has put in the effort.
For myself, I only play for my own enjoyment so when it hurts I stop, but my friend has found that re-learning a lot of his technique (with the help of a good teacher) has really helped.