...no wonder you had so much pain!....damn that’s a lot of fluid....an effusion like that isn’t normal of course, but unless you have osteoarthritis or rheumatoid, which if the imaging was clear-is not the case, maybe it’s wear and tear for all the walking and such...course I don’t know your weight but stress on the joint could cause it as well....possibly a micro-tear in a ligament?.....The doctor drained 110 cc of fluid out of my knee the first time and 30cc after my MRI so I guess that means things were improving.