If you are having mobility issues, maybe consider seeing the doc to rule out a blood clot. Usually they present with pain and redness along with the swelling, but not always. It never hurts to ask, and if it is one, it could save much grief to catch it early.
MS doesn't cause swelling directly but some of the things it does can result in the legs looking different. As the answers so far indicate, it's important to determine if one leg is larger than it used to be OR if one leg is smaller than it once was. Swelling from fluid often appears and disappears fairly quickly. Changes in the muscle usually take longer to show or notice.
Mary
Spasticity and the increased muscle tone can look like swelling. If you are havingin cramping in the larger leg, consider spasticity as a possible cause.
Bob
I have circulation issues, and my left leg is bigger than my right. I also have swelling in my right foot, because of the Betaseron.
I am no doctor.Swelling is not a direct result of MS since it is a neurological disorder. One leg can often be more muscular than another. Sometimes on your good side you can have swelling because it has to carry more weight on one side. Also it is possible to develop circulation problems as a secondary problem. Swelling in the calf would be something i would bring up with my PCP.
Alex