Regarding heat and those with Multiple Sclerosis, please see this WebMD article (one of many articles out there about this topic):
The Impact of Temperature on Multiple Sclerosis
In it is included:
"Avoid extreme temperatures. Extreme temperatures may worsen your symptoms of multiple sclerosis"
I know you're trying to help but please be careful about advising something for a condition without providing the legitimate material to back up that advice. While what you're suggesting probably won't permanently harm anyone, it can certainly worsen their symptoms and potentially increase their pain levels.
Multiple Sclerosis is not like your wife's knee pain - though I'm glad she's feeling better in that regard - or any number of other pain conditions.View Thread