Sock strangulation marks may or may not be a case of edema. If the socks themselves are too small to cause strangulation marks, they may often be caused by extrusion. Socks that are too tight can also lead to poor blood flow and cause local edema, or there may be swelling in the calf itself, so the socks may appear strangulation marks. Common causes of swelling in the calves themselves are: 1. kidney diseases such as glomerulonephritis, which often lead to water and sodium retention and proteinuria, causing hypoproteinemia; 2. liver diseases, which often lead to edema due to reduced protein synthesis by the liver; 3. heart diseases, which lead to edema in both lower limbs in patients with heart failure, as well as malnutrition and endocrine diseases, such as hypothyroidism, can lead to edema.