Sputum discharge is a chronic suppurative disease that occurs between bones and joints. After it becomes purulent, it can form an abscess near the lesion or in a distant gap. After it breaks, the pus is as thin as phlegm, so it is called sputum discharge. The "Collection of Surgery Cases" says: "Phlegm condenses in muscles, tendons, bones, and bone cavities. It is invisible and can be seen. If there is blood and flesh, it can become purulent, which is called sputum discharge." The characteristics of this disease are that it is prone to occur in bones and joints, the course of the disease is slow, it is not red or hot at the beginning, and it is late to suppurate. The pus is clear and thin, and it contains rotten cotton-like substances. It is difficult to close after ulceration, and it is easy to form sinuses. It can often damage tendons and bones and cause disability, or even endanger life. Due to the different sites of onset of this disease, there are many different names. For example, if it occurs on the spine, it is called turtle back phlegm; if it occurs on both sides of the lumbar vertebrae, it is called kidney shu deficiency phlegm; if it occurs in the ring jump area, it is called bone attachment phlegm; if it occurs in the knee, it is called crane knee phlegm; if it occurs in the ankle, it is called crooked phlegm; if it occurs in the finger joints, it is called dung beetle infestation, etc. Although the names are different, their causes, symptoms, treatments and prognosis are basically the same, so they are collectively called sputum discharge. This disease is equivalent to bone and joint tuberculosis in Western medicine.