hand or joint swelling. anyone know cause?

i know many people have had joint issues, but i havent seen if anyone has found any causes for it as this is probably the same cause. what i’m referring to is swollen joints in primarily only one hand. doctors said it wasnt arthritis or a few other things that were tested (would hve to look back)

has anyone heard anything conclusive about why joints are swollen or change colors (others have talked about other parts of body)? any theories you have would be appreciated as well.

some theories are thyroid related to blood flow issues, b12 deficiency, someone told me calcium deficiency, possibly excess estrogen?

would be nice to see omething actually happening though… like a test showing we have something specific.