What Causes Burning Sensation In Knees?

I have a hot searing burning behind my knees quite often. Sometimes just one knee and sometimes both knees. Doesn t happen everyday, but does several times a week. The pain lasts as long as 30 min or as short at 3-4 min. It is almost unbearable. I do know that I have osteoarthritis pretty much all over my body. I also have unilateral hip replacements due to it. I also have a disease called multiple endocrine neoplasy type 1. I am 63 yrs.old and overweight.