Osteoarthritis?
He's been pretty unlucky then, that usually affects older people. Maybe 50-60+.
Rheumatoid arthritis mostly affects young people, 20-50ish. If it's osteo, it's degenerative and I'm not sure there's much they can do beyond symptom treatment and replacing joints.
( my other username is a porsche , posting shit pictures so you don't have to, Thu 21 May 2009, 20:10, archived)

the doctor did say it's very rare

( Boris Johnson's Press Secretary, Thu 21 May 2009, 20:16, archived)