Knee joint effusion’s need to go to joint surgery, orthopedics, infection, rheumatology and immunology departments according to the patient’s symptoms, signs and other conditions. If the patient has a clear history of recent trauma, and knee pain, swelling, or even limited movement occurs after the trauma, the possibility of meniscus and ligament tear or fracture may be considered, and orthopedics or joint surgery may be consulted. If the patient has a history of knee joint effusion after cold exposure, accompanied by a history of redness, swelling, heat and pain in the knee joint, then consider the infection of the tissues around the knee joint, and suggest that the patient can go to the Department of Infection or Orthopaedics for consultation. If the patient has a long history of knee joint effusion or joint stiffness in the limbs, rheumatoid arthritis or rheumatoid arthritis is considered, and the patient is advised to go to the Department of Rheumatology and Immunology for timely consultation. Patients with knee joint effusion are advised to choose the appropriate department according to their own symptoms and signs, complete the relevant examinations in time, clarify the cause of the disease under the guidance of the doctor, and undergo further treatment if necessary.