I am so sorry to read you are in pain. the flu is bad enough but RA makes it worse. So, yes, the flu can make your RA flare. It is a good idea to get a flu shot early in the season if you have RA and a necessity (as is the pneumonia vaccine) if you are on Methotrexate, Enbrel, Humira or Remicade.
I thought I had the flu about 5 years ago.. turned out to be PMR and my joints were very painful.. could hardly walk.. it was in my feet and ankles, knees, and wrists..
anyway I took celery seed and Ibuprophen.. and it went into remission.. yeah! celery seed.. worked as well as the sterioids that others have been on.. and though I have had a flair up .. so has another person I know with it, who is still on the steriods..
so you might want to at least look into the symptoms.. and see what you think.