According to Right Diagnosis, cold knees are usually caused by blood flow problems. Many different conditions cause these blood flow problems, including diabetes, peripheral vascular disease and deep vein thrombosis. These conditions cause a cold sensation not only in the knee but also on the skin of the knee when the individual touches it.
Right Diagnosis lists deep vein thrombosis as a blood clot that occurs in deep veins. Although blood clots occur all over the body, these tend to cause the sensation of cold knees because they occur mostly in the thigh and calf area. This restricts blood flow in the lower half of the body, often making areas of the body cold to the touch. This problem is frequently accompanied by cold feet as well.
Poor blood circulation is one of the symptoms that accompanies diabetes, according to Diabetes.co.uk. A person suffering from poor circulation has inadequate blood flow throughout the body. This leads to a cold and sometimes numb feeling in areas of the body that are not getting enough blood flow. Diabetics usually notice poor circulation in their outer-most extremities, including the hands and feet; however, the effects of poor circulation are often felt in other areas of the body, such as the knees.