With a faster metabolism and a lower calorie intake than in winter, summer has become a great time for many people to work out and get lean. And with most people into the army of fitness, we will talk about the “sound from the knee” today – the knee popping. Many friends in doing sports will find that when their knee flexion action (such as squatting), the knee will emit a crisp popping sound, what is going on? What is the effect on our body? In fact, knee popping can be divided into two main categories – physiological popping and pathological popping. Physiological rattling is the normal physiological state. Pathological snapping is the knee joint’s “protest warning” to us. Generally speaking, physiological popping has several characteristics: First, the joint popping is not accompanied by pain or discomfort and does not affect the knee joint activities, which is the key to determine. Second, it occurs only during rapid flexion of the joint, and the popping sound is crisp, not dull or friction-like. If the above characteristics are met, it can be judged as a physiological popping sound and there is no need to worry too much. For this type of ringing, we can warm up before the activity and slow down the speed of joint flexion to adjust. If the popping sound is accompanied by pain and discomfort in the joint, and there is restricted movement and swelling of the joint after the popping sound, it is time to pay attention, stop exercising and go to the regular hospital as soon as possible.