Rheumatoid arthritis affects multiple systems, is chronic, relapsing, inflammatory and is not known what causes it. Its basically flare ups of the synovial capsule around joints. (the thing that holds the joints together) But what those flare ups do is they cause destruction of the affected joints. It is just so unpredictable because some people have mild flare ups and minimal impairment of joint functioning. While others may get totally crippled. The estimates are that 1% of the world's population are afflicted with it. And females about three times more than males. It (RA) usually affects people more in the 30-40 year age range.
Nothing is proven but RA is thought to be an autoimmune problem where antibodies (things that usually attack and kill bad stuff in our body) attack our collagen and cytoskeletal fialmentous proteins.
