Could Swelling In Knees, Legs And Ankle Be Due To Fibromyalgia?

I have been diagnosed with Fibromyalgia (a few years ago). I am experiencing a lot of swelling lately. However, I was under the impression that Fibromyalgia did not cause swelling. My hands, knees, legs, ankle and feet all swell. My PCP recently started me on steroids to help the swelling, but again, I am confused as I was told before that there is a feeling of swelling, but no ACTUAL swelling.