The reason why the fracture site will swell after the fracture occurs is that after the fracture occurs, the bone marrow cavity has to bleed, the capillary rupture on the periosteum also has to bleed, and the tear of the surrounding muscles, tendons, ligaments, and joint capsule also bleeds, and this blood gathers between the broken ends of the fracture, which will cause local swelling. After the fracture is locally stimulated, capillary permeability increases, tissue fluid exudation increases, and the entire muscle, tendon, ligament, subcutaneous, and even skin exudates and swells significantly. In severe cases, tension blisters, tension blood blisters, osteo-fascial compartment syndrome, and extrusion syndrome may occur, among others.