Has your doctor said anything to you about it?

I have some atrophy in both of my calf muscles but my doc says it is normal due to the progression of my MS.

I have weekly deep tissue massage which is considered passive exercise to alleviate some of the atrophy. When I can, I walk as much as possible but the muscles have deteriorated over time.

If you are concerned about it, I would definitely talk to your doctor about it.