Hemophilia is a concomitantly inherited coagulation factor deficiency disease. It is inherited from women who carry the hemophilia gene and affects up to half of their boys. Intra-articular hemorrhage is the most common form of hemophilia, accounting for about two-thirds of all cases, and recurrent intra-articular bleeding leads to degenerative joint changes called hemophilic arthritis. The disease is mainly manifested as recurrent intra-articular hemorrhage in childhood, and in severe cases intra-articular hemorrhage is seen at the beginning of walking. the incidence generally increases after the age of 8. with proper and timely treatment, the joint lesions can be mild or even non-existent; improper treatment will aggravate it. the incidence of intra-articular hemorrhage decreases after the age of 30. Intra-articular hematoma occurs in the knee, but can also involve the ankle, elbow, shoulder, and hip. Some people divide the disease into three phases: Phase 1 is the hemorrhagic phase: sudden acute intra-articular hemorrhage with severe pain, significant swelling of the joint, high skin temperature, significant pressure pain, restricted motion, protective stiffness of the joint, sometimes accompanied by fever, increased white blood cells, easily misdiagnosed as septic arthritis, do not puncture or incision, otherwise life-threatening, slow absorption of the hematoma, which takes 3-6 weeks. Stage 2 is the inflammatory stage: repeated bleeding in the joint, thickening of the joint capsule and synovial membrane, secondary joint swelling, restricted movement, and friction sounds during movement. Stage 3 is the degenerative stage: severe impairment of joint motion, muscle atrophy, flexion contracture deformity in the knee joint, and even severe disability. The diagnosis is difficult at the first attack of the disease. The possibility of the disease should be suspected in cases of minor trauma causing joint hematoma or previous bleeding tendency, and the diagnosis can be confirmed by laboratory tests, if the clotting time is prolonged, combined with prothrombin generation test TCT, etc. In addition to joint lesions, hemophilic cysts can be caused by subfascial, intramuscular, subperiosteal and intraosseous bleeding. x-ray examination can show normal bone quality, osteoporosis, bone cysts and joint destruction at different times. What is the prevention and treatment of hemophilic arthritis? To prevent the occurrence of hemophilic arthritis, the most important thing is to prevent bleeding in children who are prone to this disease. Attention should be paid to avoid trauma or strenuous activities in daily life, and drugs such as aspirin, anti-inflammatory pain, and botulin should be prohibited because such drugs can inhibit platelets and affect clotting. In recent years, the application of plasma containing coagulation factor VIII and coagulation factor IX can not only control bleeding, but also prevent the occurrence of bone and joint deformities. Treatment is divided into two aspects: treatment of acute bleeding and treatment of arthrosis: 1. In the case of small amount of intra-articular bleeding, the accumulated blood can be absorbed after 3-6 weeks by elastic bandage and simple braking, and then carefully start a small range of free movement to prevent contracture deformity. For larger amounts of intra-articular bleeding in the knee, fine needle puncture can be applied under the control of supplemental appropriate coagulation factors. If coagulation factors are not used for control or if control is ineffective, puncture should generally be avoided. To prevent joint ankylosis deformity, intra-articular injection of hyaluronidase can be used for prevention. For those who do not see a reduction in intra-articular exudate, adrenocorticosteroids may be added for 5-6 days. To prevent infection, antibiotics are applied systemically. For those with severe joint pain, dulcolax and codeine can be used. Patients with acute bleeding are forbidden to apply hot compresses, they should rest in bed, elevate the affected limb and apply cold compresses, compression bandages and brakes. 2, the treatment of arthrosis in adolescence in order to prevent contracture deformity, you can put the joint passive extension, and pay attention to the functional exercise of the extensor muscle, and can use a plaster splint at night. For those who have caused flexion contracture deformity, they can also be treated surgically under the control of anti-hemophilic factor.