My knees gets getting red.

It burns/tingles. My knees goes to the side of my leg randomly sometimes. Usually the redness is the first sign it's gonna pop out. So I'll quickly sit down and rub my leg and the redness will slowly go down and my knee sometimes won't pop out. Here is pictures of the random redness. It's always hot to the touch. Any ideas on what this could be?. I'll be seeing my doctor about it next week. I've been using doctor Google and nothings really come up as possibilities.

Also I wanna edit: I don't cross my legs. It usually happens while standing. Or right after standing. I'll be walking around and feel my knees tingle and start to burn so I'll sit.