Knee joint effusion extraction process firstly locate the puncture point, sterilize, enter the joint cavity to extract the effusion, and apply pressure bandage. 1. Positioning: you can locate the puncture point under color ultrasound, or you can choose to puncture on the patella? or puncture point next to the patellar tendon and mark it. 2. Disinfection: Disinfect the skin of the knee joint with iodine twice, deiodize with alcohol three times, and lay a sterile cavity towel. 3. Puncture: use a sterile syringe to extract lidocaine for local anesthesia, enter the joint cavity to extract the fluid, and keep the specimen for laboratory test. 4. Dressing: use sterile gauze and elastic bandage, avoid strenuous exercise for 3~5 days. The above is the process of knee joint effusion extraction, but also for the cause of the effusion treatment.