Could excessive heating pad use for arthritic knee lead to temporary redness?

Hi doctor,

I have been overusing a heating pad on my arthritic knee. I stopped using it yesterday because I felt like I had a sunburn on both knees. (Use on both knees as both knees have arthritis, but I have been using it more on the right knee.) I went out to sit in the sun yesterday (I did not use a heating pad yesterday), and over my knee, I noticed a red square where the heating pad usually is. I came inside, and it went away in 5 minutes. Could the two be related? I had a doctor look for thermal burns today, and he said there were no thermal burns but was unsure if the red burn that lasted 5 minutes was due to using the heating pad for the last three weeks several hours a day. And the doctor said it was weird. I think there is a strong chance the two are related. What do you think?

Thank you.

Hi doctor,

Thank you for your answer. The doctor I went to earlier kept saying the word weird. Should I stop using a heating pad? I got a Lidocaine patch to use. Should I wait another 24 hours before putting it on the knee, or is it okay to use it now if there is no evidence of thermal burn?

Thank you.