Oh my fucking god, I have rheumatoid arthritis in my knees, and I'm only 17 years old. This is what happens to your hands with rheumatoid: http://www.sciencenewsden.com/images/rheumatoid_arthritis.jpg
My only option is in 10-15 years to get total knee replacements, they won't give me replacements until I'm fully grown (both up and out it would seems). Sadly, they sometimes only last 20-30 years (30 is pushing it) and at my age, I could end up getting two or three done on both knees in my life time. It already hurts like hell to run, and now I get the news that soon I won't be able to swim anymore, one of my loved athletic activities that doesn't kill me with pain, I'm already on prescription pain killers. Why does it have to be me, or at least at my age, my grandfathers knees didn't go bad until he was 60. Bangs head against keyboard guess I'm just coming here to vent.

owwies.. sorry to hear that!
stay strong OP!