There are two main reasons for the clicking sound in the joints: first, degeneration of the articular cartilage, such as frequent excessive activity, resulting in wear and tear of the articular cartilage or menopausal women, due to menopause, the level of estrogen in the body decreases, which can also lead to degeneration of the articular cartilage. After the degeneration of articular cartilage, the degree of lubrication of the joints will decrease significantly when the joints are moving, resulting in grinding of the bones and an obvious clicking sound. Secondly, due to patellofemoral instability, after the patellofemoral joint becomes unstable, the patella is in an uneven position at the top and bottom of the patellofemoral joint, resulting in collision between the patella and patellofemoral joint due to joint instability when flexing and extending the knee joint, which will also cause a clicking sound.