I have been reading quite a bit lately about Lyme & arthritis (mainly because of my fingers, they are twisting & quite painful lately) and have come across a few sites that are worthy of posting. You'll have to copy & paste these links;
for rheumatoid: http://www.webmd.com/rheumatoid-arthritis/guide/diagnosing-ra
for psoriatic arth. http://www.psoriasis.org/netcommunity/learn_psadiagnosis
septic arth ( from INFECTION) http://emedicine.medscape.com/article/236299-diagnosis
I found this interesting, although it seems as if few acknowledge it affecting the smaller joints of the hands & feet;
"Chronic Lyme arthritis—brief bouts of pain and swelling usually occurring in one or more of the large joints, especially the knees" (http://www.acponline.org/clinical_information/resources/lyme_diseas...)
Unfortunately, there is never a 'sure thing' (speaking of cause & tx) when it comes to LD;
"Patients with certain genetic and immune markers may have persistent arthritis despite treatment with oral or intravenous antibiotics."
I hope this helps to clarify what it is. It seems that there is a whole 'nother infection that causes this.
It's been said:LD patients can be as ill as people w/ congest. heart failure & in as much pain as post-op patients.