The causes of swelling are as follows: 1, it may be local soft tissue contusion or fracture, resulting in subcutaneous or muscle and other tissues of the capillary rupture bleeding, resulting in the formation of localized swelling. Usually, in addition to swelling, there will be pain, subcutaneous ecchymosis and other manifestations. 2, may be the epidermal skin contusion, contusion bruise, resulting in local inflammation edema or inflammation exudate, resulting in local swelling. 3, may be the limb of the venous reflux is impeded, or lymphatic reflux obstruction. 4, may be the function of the degenerative diseases of old age, such as cardiac failure, renal failure or systemic low blood pressure, or the formation of the disease. There may be double lower extremity or even generalized depressed swelling in the elderly with degenerative diseases, such as cardiac failure, renal failure, or generalized hypoproteinemia.