Knowledge of the knee joint 1, the knee joint is connected to the large and small legs of the trolley flexion garrison joint. It consists of the lower end of the femur, the upper end of the tibia and the patella. Complex structure, its main function is weight-bearing, followed by movement. Therefore, the knee joint is fixed after walking is still not seriously affected. 2, patella is located in the quadriceps tendon a seed bone. The horizontal fibers of the lower part of the medial femoral muscle and the lateral condyle of the femur are very important in preventing outward dislocation of the patella. Congenital recurrent patellar dislocation is due to dysplasia of the lateral condyle of the femur. 3, the knee joint capsule is thin and tough. It is strengthened on both sides by tibial and fibular collateral ligaments respectively, and anteriorly by patellar ligament. On both sides of the patella, it is strengthened by medial and lateral patellar support bands formed by medial femoral and lateral femoral tendon membranes, and behind it, there is a fusion of national oblique ligament extending from semimembranous tendon with the joint capsule. 4, the patellar ligament is the knocking site of knee reflex, in the patellar ligament on both sides of the depression, backward can touch the knee joint space, this is equivalent to the anterior end of the meniscus, the depression disappears when the knee joint cavity effusion, the midpoint of the medial or lateral edge of the patella is the point of puncture of the joint cavity. 5.The knee joint has important structures such as cruciate ligament, meniscus and fat pad. There are two cruciate ligaments: the anterior cruciate ligament originates from the posterior part of the medial epicondyle of the femur, and travels forward and downward obliquely to the front, stopping at the anterior part of the intercondylar elevation of the tibia and the anterior corner of the lateral meniscus, which can limit excessive anterior displacement of the tibia; the posterior cruciate ligament originates from the posterior aspect of the medial epicondyle of the femur, travels forward and downward obliquely and stops at the posterior part of the intercondylar elevation, which can restrict the excessive posterior displacement of the tibia. The posterior cruciate ligament starts from the lateral aspect of the medial femoral condyle and runs posteriorly and inferiorly. 6. The cruciate ligament is an important stabilizing structure of the knee joint, which can limit the anterior and posterior lateral and rotational activities of the knee joint, and can lead to tearing or rupture of the cruciate ligament under strong force. In anterior cruciate ligament injury, the tibia can be pulled excessively towards the front of femur, and in posterior cruciate ligament injury, the tibia can be shifted excessively backward, which is clinically known as “drawer sign”. 7, the meniscus is composed of fibrous cartilage, located between the medial and lateral femoral condyles and the medial and lateral tibial condyles, the inner edge of the thin, the outer edge of the hypertrophy, with the role of stabilizing the knee joint. The circumference of the medial meniscus is connected with the joint capsule and tibial collateral ligament, the anterior end is attached to the tibial intercondylar elevation anteriorly and the posterior end is attached to the intercondylar elevation posteriorly, the lateral meniscus is not connected with the fibular collateral ligament, the anterior and posterior ends are respectively attached to the tibial intercondylar elevation anteriorly and posteriorly and are connected to the anterior and posterior cruciate ligaments respectively, and the medial and lateral meniscus are connected with the transverse knee ligaments in front of the medial and lateral meniscus. 8, in the knee joint outside the semi-flexed position, the tibia is fixed, suddenly over-rotate and straighten or over-rotate and straighten, may damage the medial or lateral meniscus, once the meniscus rupture, it can not be repaired by itself, have to carry out a meniscectomy, meniscectomy, can be synovial growth of new meniscus, but can not restore the function of the original meniscus, meniscectomy, prone to lead to the tibial plateau of the degenerative changes. 9, connected with the anterior part of the knee joint, there are four synovial bursae, namely, the suprapatellar bursa, the prepatellar subcutaneous bursa, the infrapatellar subcutaneous bursa and the infrapatellar deep bursa. The knee joint cavity is connected with the suprapatellar bursa. When the knee joint is inflamed, the exudate increases, and the liquid can fill the suprapatellar bursa, which makes the patella above and on both sides become full. If you put your hand above the patella and put pressure on the suprapatellar bursa, you can press the liquid inside the bursa into the joint cavity, and you can see that both sides of the patella protrude more, which is helpful for the diagnosis. 10, the medial meniscus is larger and thinner, “C” shape, the lateral meniscus is smaller, “O” shape, Chinese disc-shaped people appear higher than abroad. 11, meniscus will divide the joint cavity into upper and lower parts, and in the femur before and after the medial condyle to form a number of crypts, so that the joint cavity before and after the wide, narrow in the middle, when there is a septic lesion in the knee joint, the synovial membrane can make the middle of the swelling of the fissure occlusion, so in the arthrocentesis and drainage, in addition to the front of the joint to do the incision, there is a fashion need to be in the back of the joint another incision, so that the drainage of the smooth.