Patient: Description (onset, main symptoms, hospital, etc.): boy 6 years old, two months ago, knee swelling, the hospital to check the fluid, after that, antibiotics, take the drug Nebulizer after the child may be less painful, continue to walk, and so on, once the drug stopped, found that the joint swelling, can not get out of bed, swelling, pain, hand mold joint heat, go to the hospital, ultrasound, CT, the doctor said soft tissue swelling, antibiotics for more than 10 days, no improvement, and then hospitalized, testing: MRI: there is fluid, synovial wall thickening, DNA tuberculosis (negative), puncture fluid culture bacteria twice (no bacterial culture), DNA tuberculosis. After the hospitalization, the tests were performed: MRI: fluid, synovial wall thickening, DNA tuberculosis (negative), puncture fluid culture bacteria twice (no bacteria culture came out), puncture fluid pus ball degree (3+), rheumatoid rheumatism excluded, immune problems, arthroscopic examination of synovial wall debris cleaning, but not much, postoperative gentamicin drainage for 2 days, 7 days after the removal of the drainage tube, the joint swelling again, blood sedimentation 90, CRP 30, antibiotics for 20 days, no significant effect. Is it possible that it is septic arthritis, or reactive arthritis? Lou Yue, Department of Orthopedics, Nanjing Children’s Hospital, Nanjing Medical University: Pus ball 3+ is definitely a septic infection. Bilateral septic infection of the knee joint is rare, and it is important to consider whether there are other primary diseases on which the infection is co-infected. It is recommended that effective antibiotics be given continuously intravenously for 3 weeks, and oral antibiotics be given for 3 weeks after continuous negative blood sedimentation and CRP. Patient: Thank you, he is right knee monoarticular swelling pus cell puncture fluid test (++), both punctures are the same, fluid DNA tuberculosis negative, antibiotics before surgery for about 20 days, another 10 days after surgery, arthroscopic cleaning without too much debris, cleaned some blood tissue on the synovial membrane, nothing granulation tissue. Now, the drainage tube has been removed and there is almost no fluid in the joint, but the soft tissue is still very swollen. I would like to ask a few questions: 1, pus cells ++++, but no bacteria can be cultured (twice), is it related to the previous antibiotics; 2, arthroscopy cleanup, post drainage for 3 days, gentamicin, until it comes out significantly less than it went in, after a day or two the joint is swollen again, hot? Temperature is just a low fever 37.~37.7 3, how can I rule out whether reactive arthritis is also present, because I think, at the beginning of the month is not so strong, but the child can not sit, walk all the time, ride a bike, until after stopping Nebulizer know that it is very serious. 4. Is the antibiotic dosage insufficient? I’m asking you, is it possible that reactive arthritis without attention and maintenance will be puncture fluid pus cells +++? Nanjing Children’s Hospital, Nanjing Medical University, Department of Orthopedics Lou Yue: Now it should be septic arthritis. The culture is often negative after antibiotics are used. Reactive arthritis joint fluid should be clear and transparent, and pus cells are unlikely to be 3+. If the joint surface is red, swollen, hot and painful, indicating that there is still inflammation, treatment of diphtheria or more effective antibiotics continuous intravenous drip, lower limb skin traction brake, coupled with supportive treatment, usually 2 weeks later there will be significant results.