I am a therapist who works in geriatrics, and I feel for you ladies. If your doctor says its OK, I seriously recommend taking fish oil. The Omega 3s can really help inflammation and while they can't replace the worn down tissue (Cartilage) it can help the pain quite a bit.
It also has other nifty benefits for your heart and your brain (it can really cut your risk of dementia!)...look into it!
As far as lasting heat, the paraffin can really help, it seems to penetrate pretty deep and those home spa things can be a good investment.