Thanks @mrmie ! I was actually tested for Lyme as part of my massive panel and it was negative. The only other items that came up were slightly elevated Calcium and Albumin (by slightly I mean .1 over the range). I did find an article that reactive arthritis can be caused by an infection in another part of your body (most often your intestines, genitals or urinary tract) but I'm not sure if this is a stretch (arthritis is in my family history). Thanks for the links, I'll take a look!