Cold knees can be caused by lack of activity, knee joint disease, lower limb vascular disease or physiological reasons. 1. Lack of activity: lack of activity and exercise can lead to slow blood circulation in bilateral lower limbs and insufficient blood supply locally, which can cause cold knees. 2. Knee joint disease: after knee joint trauma, knee replacement and other surgeries, due to the wounds and surgical incisions at the knee joint, it can lead to the destruction of the local capillary network, and the number of local blood vessels that can supply blood is obviously reduced, which can lead to the coldness at the knee. 3. Lower extremity vascular diseases: lower extremity atherosclerosis occlusion, lower extremity arterial embolism and other vascular diseases can lead to narrowing of the vascular lumen, reducing the elasticity of the blood vessels, resulting in blockage of local blood circulation and insufficient supply of blood to the knee joints, which can lead to coldness in the knees. 4. Physiological reasons: prolonged exposure to cold and damp environment, or too thin clothing at the knee joints can lead to long-term cold attack on the knees, resulting in the performance of cold. When the knee is cold, you should consult a doctor in time, and under the guidance of a specialist doctor, you can actively carry out the appropriate treatment, which will help to alleviate the discomfort symptoms as soon as possible.