Knee joint cavity puncture is a commonly used puncture method. The knee joint cavity puncture site consists of four points: external superior, external inferior, internal superior, and internal inferior. First of all, if we take the external superior as an example, we should position the knee joint puncture point so that the knee joint is slightly inwardly turned, because the normal knee joint is outwardly turned, which will affect the joint puncture. In addition, the upper edge of the patella and the lateral edge of the patella, for example, are the entry points for puncture. During the puncture, the puncture needle should be kept at 45 degrees to the joint surface, so that the first advantage is to reduce pain, the second is to avoid excessive bleeding, and the third is to avoid touching the cartilage surface of the joint.