The disease called “old rotten leg” is mainly a chronic skin ulcer in the lower part of the lower leg. At the beginning of the disease, it may only be inflammatory exudation, and then ulcers occur, and the old does not heal, the bigger and deeper the rotting, and eventually the whole layer of skin is rotten. The skin around the ulcer is affected and atrophied, darkening, causing eczema, flaking from time to time, and itching. Once the ulcer occurs, the bone is exposed and the surface becomes infected, resulting in chronic osteomyelitis. Some patients are suffering for years or more than a decade. Humans are walking upright, lower limb venous blood flow back upward must overcome a great deal of geocentric suction. The mystery of this is mainly the pressure difference between the arteries and veins. The former pressure is high, the latter pressure is low, the direction of blood flow naturally from high to low and travel. In addition, there is the squeezing effect of muscle contraction when the lower limbs move, as well as the static membrane valve located inside the vein. Some people are born with weak vein walls, or the number of static valves is too little, poor structure, poor function; if usually standing still, the lower limb muscle activity is reduced, the muscle squeeze effect is not enough, the lower limb venous blood flow back is blocked, causing the pressure in the veins to rise. After a long time, the superficial veins of the lower limbs expand and thicken, and then develop to twist into a group, like a group of earthworms coiled under the skin. Patients often feel soreness and fatigue in the lower limbs, and some have edema in the back of the foot or ankle joint. If left untreated, the skin of the lower leg and ankle will become atrophied, thinner and brighter, with sparse sweat hair, darker color, eczema, and even ulcers.