Middle Finger Knuckle and Finger Swelling

Hi all

Have had this for around 2 months with Arthritis, Kidney/Liver and bone issues ruled out via blood tests and e-rays.

Middle finger knuckle is red/purple and finger generally swollen. Knuckle can be very sensitive if hits of anything and there almost appears to be a small growth on the left side of the knuckle which is not bone given x-ray has a week ago would have showed up. Dr does not seem to have an answer?

Anyone able to assist?

possibly gout or pseudogout.

Thanks, Dr has ruled our gout and did not mention pseudogout