“My knees are on fire” my wife said to me the other month when we were on a shopping marathon. I used to think she was a bit dramatic, but now I totally respect her very keen perception of what was happening in her knee. Researchers from Cambridge University found that thin, diseased joint fluid from arthritic knees causes activation of the same nerve fibers found in your mouth when you eat hot peppers. Researchers took the thinned and damaged synovial fluid from human volunteers with known arthritis and compared it to synovial fluid from normal cadaver knees without arthritis. First they found that the fluid from the arthritic knee had lost its normal properties to cushion and lubricate the joint. However, when they placed it with some nerves taken from mice, they found that the damaged joint fluid from arthritic knees stimulated the same nerve we have in our mouths when eating hot peppers. This nerve is called the TRPV1 receptor sometimes known as the capsaicin receptor because it senses the heat of spicy food and gives us the feeling that something is hot or scalding. As much as I hate to admit it, my wife was totally right. Her knee did feel like it was on fire!