Lyme arthritis is one of the gifts that I have been graced with thanks to my infections.
It acts just like Osteoarthritis, damaging joints and the inflammation, but it doesn't have 'markers' like Osteoarthritis that show up in blood work. My fingers and toes were twisting and bowing like I had advanced Osteoarthritis! Some of that has gone away with treatment, but once the joint has been damaged, it's damaged.
If you've hit a plateau in your healing and you are detoxing (including using the detox baths described in our "New to Lyme?" thread), then other tick-borne infections need to be considered. They usually stop progress in a person's Lyme treatment. Another thing, has your doc switch abx in your treatment? That might be another option that could be tried to 'jump start' your healing again.