Rheumatoid, lupus, limes disease -impairment in synovial membrane. cause unclear. auto-immune. body attacks itself. membrane infected and swells, painful, flud gets think, gunky so things don't move well. redness and heat at site. big knuckles, point to side. RA affects any age, more disabiling than osteoarthritis, destroys tisse. can reach lungs, eyes, heart, brain. comes and goes. can be acute.