There are several common causes of knee rattling during exercise: First, the patella is not running properly, and the patella moves outward, causing abnormal wear and tear on the patella and femoral condyles, which can easily cause knee rattling during exercise. Second, sudden twisting of the knee joint during exercise, wear and tear between the femur and tibia can occur, causing ringing in the joint. Third, patellofemoral arthropathy, patellofemoral joint is formed by the patella and femur slide, when the patellofemoral joint is inflamed, cartilage damage can occur, the cartilage surface is rough and uneven, which can cause the knee joint to rattle and pain during exercise, which can seriously affect the patient’s movement of walking up and down stairs and squatting. The above three conditions are common causes. Treatment includes exercising the quadriceps strength, correcting the patellar trajectory, avoiding sudden twisting movements of the knee joint during exercise, and if serious damage to the articular cartilage occurs, which affects joint movement, early knee arthroscopy can be performed to repair the joint surface.