The crunching sounds may be crepitus...this is a sound joints make as they dry out, as in osteoarthritis.
My neck has really become stiff lately and I have these sounds too. I don't have MG. I think my trifocals are a bit at fault too.
The most common place you can hear this is in the knees.
Have your doctor do an Xray... any arthritis or disc changes may show up that way. An MRI is more expensive but shows more detail. But you may not need one if the Xray shows "stuff".
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Weezie looking at petunias 8.25.2017
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