These are hard to know. I have cysts and lesions in and around my lower spine. I have small fiber neuropathy diagnosed via a skin punch test. In my case, I had similar symptoms in different joints. Consider any trauma to your body via viruses, surgery or bacterial issues to see if those may have contributed to your current symptoms. In my case, I had a malabsorption problem from abdominal surgery 7 years ago and the lack of vitamins/minerals that are absorbed in the lower intestines resulted in nerve damage. It took 4.5 years of doctors to get the proper diagnosis. Now that I know the underlying cause, I can address it. I’m getting better. Small fiber nerves can regenerate. It ain’t easy but if you find out the “why” you have a shot at reversing it. The odds are not great and many cases are ideopathic, but I can tell you it can be solved. Best of luck and I hope this helps. Btw, cut out sugar, gluten and dairy. Very inflammatory. PS. The back problem could be it. Welcome to the journey 🙂