arthritis hot

What disease can cause the knee to be sore and warm during sleep (while the rest of the body's normal temperature)?
Medical a friend was unable to determine what is wrong, and blood tests do not detect rheumatoid arthritis. There was no injury to the knees. She is 20 years and only woke up one morning with aching feet and sore knees now.
I am not a health professional, but as I have been suffering from the same ailment, I am of the opinion that too much uric acid can also cause your knees to be sore and hot. You can try some diuretics and common see if you are using the same type of food for long periods, which can also increase uric acid.
