I have to keep my knees seriously warms. (Chondromalcia patellae.) Like body temperature warm. I was told 45 years ago that if I didn't, it would be knee replacement time. So I over-dressed my legs.
18 years ago I had this thought - what if I invented some really warm warmers that covered just my kneecaps and far enough around to protect them from wind. So I designed pads using two layers of 300 weight windproof fleece, light elastic straps around the backs of the knees and velcro straps that run up to "D" rings I sew into all my shorts at the hem. I wear whatever I would wear anyway over them. (Regular kneewarmers up to mid 70sF.) I had a local shoe and outdoor clothing repair shop make them. Cycling life changers.
PM me if you want patterns. I think I can still find them.