Lately my patients have been asking me a variety of questions about the knee, some about the treatment of osteoarthrosis of the knee and others about knee arthroplasty. The questions cover a wide range of topics. I often answer individual questions, but as patients’ medical knowledge continues to improve, so does the depth and specialization of the questions they ask, so I think it is necessary to give a comprehensive answer based on the content of the questions patients have asked in the past, so that the majority of joint surgery patients can have a fuller understanding. In the future, I will answer the questions in stages. Wen Licheng, Department of Orthopaedics, Peking University First Hospital I. What is the need to replace the artificial knee joint before answering this question, first of all, I would like to briefly introduce the basic knowledge about the knee joint, in order to the majority of patients are able to read and understand, I will try to avoid the use of too specialized vocabulary in the introduction. 1, a brief introduction to the normal structure of the human knee joint: the knee joint is made up of the femur at the lower end of the femur (the thigh bone) and the tibia at the upper end of the tibia (the lower leg) and the patella. As well as the patella, they are in contact with each other the surface of the bone covered with cartilage (often called brittle bone), by four ligaments to connect them together, between the inner and outer each have a meniscus, because the shape of the half-moon so called meniscus. The knee is an important joint in the human body and is used every day from birth to walking. Under normal circumstances, the human body in the activities of the knee joint mutual activity is the surface of the bone cartilage to cartilage activities, cartilage has elasticity and wear resistance. 2, the knee joint why easy to problem: to answer this question is more complex, involves more things, I can only briefly. For young people due to sports trauma caused by bone and intra-articular injuries caused by arthropathy here will not say more, I mainly introduce the middle-aged and elderly people are often problems. Some literature reports that the incidence of osteoarthropathy of the knee is as high as 50% or more in people over the age of 60, and I feel the same way when I see patients in the outpatient clinic. Many middle-aged and elderly patients often tell me that they have joint pain when going up and down the stairs, squatting, and even walking on level ground, and some patients need to hold a crutch in order to walk, in fact, these patients are suffering from osteoarthropathy of the knee joints, which is a professional diagnosis, and in layman’s language, it is due to the wear and tear of the joints caused by the use of the joints over a long period of time. When it comes to wear and tear, it’s easy to understand. Anything used for a long period of time will have wear and tear, and human joints are no exception, and the human knee joint is relatively special. The degree of wear and tear is generally related to two things, namely two “quantities”, one being the amount and the other being the weight. Quantity is easy to understand, the more you use it, the more it wears out. And the weight of the general public is not very good to understand, I said here is the weight of the weight of the human body, the human knee joint development and maturity, women in about 18 years old, men in about 20 years old. At this age weight tends to be relatively light, especially in this period of time some girls weigh about 90-100 pounds, but after 40-50 years of age, some in the marriage and child birth weight gain a lot of weight, up to 140-150 pounds, or even more. The increased weight puts great pressure on the knee joints, and the wear and tear on the knee joints during daily activities or general exercise can be several times that of normal weight. Imagine what it would be like to be 100 pounds younger and 150 pounds heavier in middle age and walk with 50 pounds of weight every day. I often see this in outpatient clinics, and the degree of wear and tear on the knee joints varies greatly depending on the weight of the patient at the same age. Most of the patients I have performed knee replacement surgery on in my ward were overweight. Of course, in addition to the two quantities I have mentioned above, there are other concomitant factors, such as uneven stress on the joint surfaces due to O-legs and X-legs, joint instability due to ligament damage within the joint, and unevenness of the joint surfaces due to fractures within the joint, which can also cause excessive joint wear and tear. So what is the result of knee joint wear and tear, first of all, the cartilage within the joint is damaged, and cartilage is a very special tissue, it itself does not have blood circulation, that is to say, it does not rely on the blood supply of nutrients, it relies on the joint fluid to provide it with nutrients, so the cartilage within the joint is damaged, the recovery will be very difficult. Long-term repeated friction on the joints, as well as trauma and overweight will lead to cartilage tissue from the surface damage → deep damage → cartilage disappearance → joint space narrowing → joint “bone to bone” friction → hardening of bone surfaces in contact with each other → bone proliferation around the bone surfaces of the joints, due to “bone to bone” friction produces a lot of bone. Due to the “bone to bone” friction, many bone particles are generated, forming intra-articular free bodies, and these small free bodies will invade into the joint space to form similar to the sand in the eyes, which will aggravate the wear and tear of the joints, and due to the increasing number of bone wear particles, they will also gather together to form larger free bodies. Many patients often have the misunderstanding that it is the long “bone spurs” in the joints that lead to joint problems, but in fact it is the joints that have problems that grow “bone spurs”, that is to say, when you take a radiograph and find that there is osteophytes in the joints, the cartilage in the joints must have a considerable degree of wear and tear. That is to say, when you find osteophytes on radiographs, the cartilage in the joint must be worn out to a considerable degree. We call this disease osteoarthrosis of the knee or osteoarthritis, but the meaning is the same. In the early stages of the disease, joint pain only occurs when walking up and down stairs or when squatting, but it gradually worsens with time, and pain occurs when walking on level ground, while the range of motion of the joints gradually becomes smaller, even affecting squatting. My patients often tell me when they see me that they can walk on level ground, but it is very difficult to go up and down the stairs or squat, especially on the higher steps, which are almost impossible to go up without the help of other things. This is a typical symptom of patients in the middle and late stages of the disease, and further development of walking on the ground also need to use a cane to help, and this disease during the day the pain is still relatively mild, and at night the pain will be aggravated. This disease has a great impact on daily life, seriously affecting the quality of life of middle-aged and elderly patients, and in recent years the number of outpatient visits has increased year by year. (I)