The knee joint is the body’s main weight-bearing joint. Prolonged or excessive use, or trauma, can cause cartilage damage and bone loss in the knee joint, resulting in increased friction between the bones and swelling and pain. But why do some people still get the disease when they are so concerned about protecting their joints? Who is more likely to get degenerative knee disease? The first cause of knee degeneration is aging. Just like wrinkles on the face, the joints and organs of the body will age as we get older. Among the many joints, the weight-bearing joints are the most susceptible to aging, such as the knee and hip joints. As we age, the rate of disease increases rapidly due to the loss of nutrients in the knee cavity, the accumulation of years of wear and tear, and joint inflammation. Most older adults over the age of 65 are affected, while 80% of people over the age of 75 are affected. Excessive activity and trauma can accelerate knee wear Excessive activity is another factor that contributes to degenerative knee disease because the various cartilage surfaces within the knee joint, as well as the meniscus, are limited in the number of times they can withstand friction during their lifetime. If a normal person walks 10,000 steps a day, the knee joint experiences 10,000 times of friction. If there is too much exercise, or if the knee joint is bent too much, then the knee joint will experience severe wear and tear. Therefore, people who are overly physically active will develop degenerative knee disease earlier, such as athletes and mountain climbers. These people are also prone to trauma, such as meniscus and ligament damage. If the ligaments are unstable and the meniscus is uneven, the leg will wobble when walking, speeding up wear and tear; or they may be stimulated by inflammation and develop recurrent synovitis, which causes a large amount of fluid to accumulate in the joint cavity, preventing the joint cartilage from absorbing nutrients and leading to cartilage degeneration. Perimenopausal women are more likely to get degenerative knee disease. The decrease of estrogen is one of the factors that accelerate the degeneration of the knee joint, so perimenopausal women are more likely to get osteoarthrosis of the knee joint. There are two main changes in perimenopausal women. The first is that estrogen loss activates osteoclasts, whose task is to “eat” bone, resulting in lower bone mass and osteoporosis; the second is that there are estrogen receptors on the surface of articular cartilage cells, and estrogen can improve the muscle strength of skeletal muscles and provide nutrition to articular cartilage. When estrogen decreases, the cartilage loses nutrients and gradually becomes erosion and the cartilage surface is no longer smooth, resulting in increased friction and degeneration of the knee joint. In addition, obesity also increases the burden on the knee joint and increases wear and tear on the joint surface, so obese people are also prone to osteoarthritis of the knee. In addition, degenerative knee joint disease is also related to their own genetic changes, about 4-6% of osteoarthropathies are genetically determined, which explains why some people pay attention to protecting their joints, but still have osteoarthropathies of the knee.