The ultrasound performance of the normal knee joint mainly includes the following aspects: 1, frontal observation of the suprapatellar bursa and quadriceps tendon, the suprapatellar bursa has no effusion, no synovial hyperplasia, etc.; 2, observation of the medial area, the lower end of the femur and the lower end of the tibia are normal in terms of bone quality, and the bone quality is in a continuous and smooth state; 3, meniscus in the medial area and the lateral area are triangular in shape and regular in morphology, and medial and lateral collateral ligaments are in the normal echogenicity area, and bone is in the obvious strong echogenicity area; 4, the popliteal fossa in the dorsal area is not effusive.