I had torn cartilage in one knee and found that the castor oil pack helped
it. I didn't warm the pack, I just made a small one and then wrapped it in
plastic wrap around the knee. It helped with the pain - sometimes. I
do a lot of walking and the knee eventually got worse so then had surgery to
"repair" the cartilage which made it even worse yet and a couple of
months later had knee replacement. (I've had both knees replaced.) Found
during the recovery process that the castor oil packs helped a lot.
It has taken a while for the knee to become fully functional/recovered from
the replacement but I'm walking as much as I ever did before even the first
replacement. I do 3 to 5 miles a day with no discomfort. The only
thing I miss is that I'm unable to jog.