The knee joint is one of the most used joints in humans because one of the hallmarks that distinguishes us from other mammals is walking upright, making the knee joint, located in the middle of the lower extremity, one of the joints with the greatest range of motion and stress in ordinary life and sports. As a result, the knee joint has also become one of the most vulnerable joints to injury. Our knee joint has developed a very complex structure to accommodate its important and complex functions, but it has only two basic and important functions: weight bearing and flexion/extension. Weight-bearing mainly refers to bearing weight and completing functions such as walking, running and jumping; flexion and extension mainly refers to completing functions such as walking up and down stairs and squatting. I think we need to know: the knee joint consists of three bones: the patella in front, the proximal femur and the distal tibia. The joint between the femur and tibia is called the tibiofemoral joint, and it is not only these two bones that carry the weight, but more importantly the smooth and intact cartilage on the surface of the two bones and the crescent-shaped meniscus on each side. As you can imagine, if one of these components is damaged, especially if it is serious, it will affect the ability to bear weight. The main clinical symptom is pain when walking or lifting heavy objects, mainly on both sides of the knee. The patellofemoral joint, which is composed of the patella and the front part of the femur, is the main weight-bearing structure between the two, except for the bone, which is the only cartilage. Therefore, once the cartilage is severely worn or traumatically damaged, pain may occur when walking up and down stairs or squatting. Clinically, the pain is usually in the anterior aspect of the knee joint. With this knowledge, we can have a general understanding of our own knee pain. If the pain occurs when going up and down stairs, squatting on the toilet, or standing up after sitting for a long time, it is often a pain in the patellofemoral joint, which usually means that the patellofemoral cartilage has been more obviously damaged; and if the pain is on the inside or outside of the knee joint when walking, running, or lifting heavy objects, it is usually caused by damage to the tibiofemoral cartilage or meniscus. At this time, we need to minimize or avoid actions that cause significant pain in order to protect the corresponding parts of the tissue and reduce further damage. Otherwise, if left unattended and unprotected, the cartilage tissue may be worn away and eventually irreparable, and the only option is to have an artificial joint replacement. I think this is not what the patient wants nor what the doctor wants. Of course, it is still best to see a sports medicine professional as early as possible. They can give you the best treatment plan and protection plan that will slow the progression of the disease as much as possible and reduce the chances of eventual joint replacement surgery.