Generally, there are special warm-keeping appliances to keep warm. If it is not particularly cold in winter, you can add a knee pad inside. Even if some knee pads are thin, this extra layer at least protects the knee. If you like sports in winter, you'd better wear a little thinner, because too thick knee pads will affect the activities of joint parts. Exercise generates heat. If it is too thick, it is easy to make the joints sweat. If you feel uncomfortable, take off your knee pads, and you will catch a cold more easily.
If you don't like knee pads, you can sew more cotton on the knees of thermal underwear, or add a cotton pad specially. This will not make your knees feel particularly uncomfortable because you take off your clothes. In winter, people's activity ability is also limited. If you don't exercise for a long time and only rely on clothes, food or small sun fireballs to keep warm, it is better to exercise a little and let your body dissipate heat. You can wear airtight outer pants in winter, so that cold air will not easily penetrate the clothes and freeze to your knees.
For comrades who can't sleep well at night, I still suggest that you wear a pair of warm knee pads when you sleep at night. Pushing the quilt when sleeping will not freeze your knees. I like to put my legs out when I sleep in winter, but it's certainly not particularly cold. Although it is not very cold, it is easy to freeze after sleeping for a long time.
Knee antifreeze is generally wrapped in antifreeze, so don't let your knees face the biting cold wind. You can put a heating sticker on the clothes inside your knees indoors. It is available in the market and it is said that it is not very expensive. You can also soak your feet with hot water before going to bed to speed up blood circulation in your legs and help keep your knees warm.