As defined by the American College of Rheumatology in 1986, osteoarthritis is a group of diseases characterized by: (1) destruction of articular cartilage integrity; (2) lesions of the subchondral bone plate; (3) osteophytes at the joint margins; and (4) signs and symptoms. I. What is articular cartilage integrity disruption? A joint is formed where one bone joins with another bone. Each end of the bone of the joint is covered by a layer of articular cartilage, with synovial membrane and joint capsule, and muscle attachment. Below the articular cartilage is a thin layer of hardened bone called the subchondral plate. The articular cartilage can be seen through X-rays, so we cannot see the cartilage on X-rays, and the bone at the end of the joint is the subchondral plate. The articular cartilage is made up of hyaline cartilage, which is composed of two main types of chondrocytes and matrix. Chondrocytes account for only 1%. The matrix accounts for 99%. The matrix is dominated by collagen fiber type II, which accounts for 50%, and extends from the subchondral plate to the cartilage surface in a reticular arrangement, and another 30% is mucopolysaccharide, which is dominated by hyaluronic acid. When the joints are active or weight-bearing, the cartilage is squeezed and the water in the mesh structure can be squeezed out; when it is not weight-bearing or resting, it absorbs enough water from the synovial fluid secreted by the synovial membrane like a sponge, and thus gets the nutrients. When the human body tends to age or suffer from trauma or disease, the type II collagen fibers in the articular cartilage degenerate and gradually break and become shorter, causing the articular cartilage to lose its elasticity, followed by cracks, blisters, erosions and ulcers, making the cartilage surface brush-like and rough. The unsmooth cartilage surfaces rub against each other, further aggravating the cartilage damage. At this point, the integrity of the articular cartilage is destroyed. Second, the lesion of the subchondral plate means that the lesion is further developed The early lesion of the disease is concentrated in the cartilage, the thickness of the cartilage is changed, the surface smoothness is lost in a brush-like shape, or the cartilage surface is peeled and ulcerated. With the development of the disease, the cartilage shedding makes the subchondral bone plate exposed, and cystic changes of different sizes can appear under the cartilage bone plate, these cystic changes can also penetrate the bone plate to break into the joint cavity, making the articular cartilage surface more mutilated, at this time the lesion has extended from cartilage to bone tissue, suggesting further deterioration of the disease. Third, the joint edge osteophytes can be detected on x-ray The pathological changes of osteoarthritis are not only limited to cartilage and bone tissue, but can also affect the synovial membrane and ligaments and even the joint capsule. Both synovial and ligamentous lesions can cause osteophytes to develop at their points of attachment, and because both the sites of attachment and the locations of the growths are at the edges of the joints, lip-like osteophytes can be seen on x-rays. Because the joint capsule and ligaments are constantly stretched during decades of joint activity in humans, osteophytes with bony attachment points can also occur and cannot be diagnosed as osteoarthritis on this basis. The presence of osteoarthritis must be accompanied by symptoms and signs. In principle, osteoarthritis can occur in all joints of the body, but systemic osteoarthritis is most common in the finger joints and local osteoarthritis is most common in the knee joints. Osteoarthritis of the fingers is multiple and is more common in middle-aged women, mainly involving the distal interphalangeal joints; it is less common in men, mainly involving the proximal interphalangeal joints. All have a family tendency to run in families. In women, for example, osteoarthritis of the fingers is characterized by stiffness and pain in the finger joints in the morning, which improves after a few moments of activity. Gradually, symmetrical bulges appear at the interphalangeal joints of the fingers and gradually form nodules called nigrostriatal nodes. Eventually, finger deformities and sometimes small cysts develop. The familial tendency is very pronounced. Osteoarthritis of the knee can be unilateral or bilateral, and is still prevalent in women, who are often overweight. Symptoms appear in middle age when walking from a seated position with knee pain and discomfort that disappears after a period of walking, which is the clinical manifestation of early knee osteoarthritis. As the disease progresses, it is found that activity does not relieve the pain and there is some difficulty in going up and down stairs, squatting and getting up from a seat, requiring a hand on the knee to support it. There was also some swelling of the knee joint after more walking, and in some cases the knee was so swollen that some yellowish fluid could be drawn out. Due to the thickening of synovial membrane and joint capsule with lesions, there can be a ringing sound when moving. If there is free body formation in the joint, it can affect the joint movement and there is joint strangulation from time to time. In the end, knee deformities may occur, such as knee flexion contracture, O-leg or X-leg, and even crutches to walk.