The mechanization of hematoma is usually within three weeks of the injury, whether it is due to subcutaneous bleeding caused by a fracture or caused by a soft tissue injury, it will start to coagulate and turn into a blood clot within 6-8 hours. If there is more localized necrotic tissue, there is a chance that localized sterile inflammation may be triggered, resulting in localized redness of the skin, a slight increase in skin temperature, localized swelling, and significant pain. If the swelling is large enough and the internal pressure increases, or after the application of some symptomatic drugs and suitable treatment, the bleeding will gradually stop and the swelling will not increase any further. The hematoma in the soft tissue will first be partially dissolved and absorbed by the surrounding tissues, or after separating it, it will be discharged with the circulation of blood and body fluids, and the remaining necrotic tissues that cannot be dissolved and absorbed will be absorbed and phagocytosed by the new tissues. Minor injuries may not leave visible subcutaneous hardness and scarring, or scarring that is relatively small in extent will be replaced by new tissue. If the injury is severe, a long-lasting hard scar may form and the elasticity of the tissue in this part of the body decreases, and the more severe the injury, the larger the scar will be and the less likely it will be absorbed.