I have si joint dysfuction and when my lower back and hip starts to hurt my legs swell. The doctor said she not sure if its from my si joint dysfuction that is causing this. I try to take advil and not my pain medication and she told me to stop taking it that it causes swelling.. I have stoped taking it for a week and i'm still having problems but i never asked her why does it cause swelling.. don't go back to see her for 3 months and i would really like to know why