joints were hurting him and condition has severely worsened

Hello,I have a male friend who lives in Grand Junction,Colorado. He is white, 47, 5' 10" , 247lbs. He works with sheet metal. Last Sept., he & his wife visited us in Henderson, Nevada. He was commenting about how his joints were hurting him, and he thought maybe he had aurthritis. Now, he cannot drive, put a shirt on,or walk for very long. He says he feels like the tendents in his wrists,& back of his legs are being cut with knives. He has had numerous blood tests, and been examined several times. ( 4 doctors ) No MRI yet.He tried, but the pain from laying on the table was so intense,he couldn't stand it. Is it possible he could have some kind of parasite? Before this, he was working at the jail in Grand Junction. He has had testing for reumatoid authritis, but negative. His condition has severely worsened since last October. We are at a loss as to what to do next. Thank you so much !