Patellar effusion claim does not exist, should refer to the knee joint effusion, a small amount of knee joint effusion can mostly be self-healing, when the accumulation of excessive fluid is difficult to self-absorption. The knee joint is the largest and most complex synovial joint in the human body, and a certain amount of lubricating fluid exists in the joint cavity itself, which plays the role of lubricating the joint. When the knee joint is stimulated by factors such as injury or disease, which triggers an inflammatory response, more exudate may appear in the joint cavity, which may result in the accumulation of fluid in the joint cavity. If the joint fluid is relatively small and there is no obvious swelling or pain, the joint fluid can be absorbed by itself after braking and resting. If there is a lot of fluid in the joint cavity and the joint is swollen and painful, which seriously affects daily activities, the fluid in the joint cavity usually cannot be completely absorbed by itself, and timely medical treatment is needed, such as knee joint puncture. Knee joint effusion, regardless of the amount, is a manifestation of the existence of pathological reactions in the joint, should be consulted to clarify the cause, to avoid delay in the condition.