What’s wrong with my knee always rattling inside? What is the reason for the knee always rattling? Many people will hear a crunching sound when they suddenly straighten their knees after sitting for a long time, but after the sound there are no other uncomfortable symptoms, which makes people troubled, is this phenomenon is normal? Is this normal? Is there something wrong with the knee? The knee has a ringing sound, may be the joints in the “oil” is not enough joints, like clasping hands; clenched fist of the hand (joint head), is wrapped in the other hand (joint fossa), in order to reduce the friction between the two hands (two bones), there is a certain gap between the two hands (joint cavity), in the gap filled with synovial fluid, can play a role in lubrication. It can play the role of lubrication. This synovial fluid does not always exist, but is constantly renewed and replaced. When the joint moves, it squeezes the synovial membrane, which produces synovial fluid and lubricates the joint. If you do not exercise and do not “squeeze” the synovial membrane often, the synovial fluid in the joint will become less, and the lack of lubrication of the joint will always emit a “click, click” sound, and this sound will make you feel like the knee is being rubbed. The medical term for this is “knee popping”. When a young person squats or goes upstairs, the knee clicks and clatters, mostly because the kneecap (the bone that protrudes from the front of the knee when the leg is flexed, called the patella) has moved inward or outward. When bending the knee, the muscles on both sides of the knee are like a tug of war, fighting each other to pull the kneecap towards them. If the muscles on the inside of the knee are too tight, they will pull the kneecap inward; if the muscles on the outside are too tight, they will pull the kneecap outward. The muscles on the side that are “strong” will “lead” the kneecap (the kneecap will shift to that side) and also hit other tissues, making a “click, click, click” popping sound. How can you determine if the popping is caused by a shifting kneecap? First feel the kneecap, let your legs relax and straighten, you can easily see two nests in the knee, the bone in the middle of the two nests is the kneecap. You can ask a friend to help you, push the kneecap to the outside all the time, then you squat down and see if the knee still pops; if it does, have a friend push the kneecap to the inside all the time, and you squat down again. When you squat twice, as long as one of the pops disappears, you can be sure that the pops are caused by the kneecap moving inward or outward. If the joint rings like this, nothing is wrong The joint cavity is filled with synovial fluid and there are no gaps (like glass glue between two tiles, there is no air between them and the inside is under negative pressure), which keeps the parts of the joint close together and keeps the joint stable. But when the joint suddenly moves, the negative pressure is disrupted and a small amount of gas enters the inside of the joint cavity (suddenly someone has to separate the two tiles and air enters between the glass glue). These gases will spread to all parts of the joint cavity, and also with the synovial fluid vibration, emitting a loud sound, this sound is called physiological popping, no harm to the body. What kind of sound is “physiological popping”? Crisp, discontinuous sound: The joint ringing is particularly crisp and discontinuous, and there must be a period of time between ringing. Often occurs when a joint suddenly moves: Physiological popping is a sound that occurs when a joint is suddenly pulled or bent. No pain in the joint after the ringing: When this ringing occurs, the joint feels a little uncomfortable, but after the ringing, the joint feels much easier and no pain occurs. Will the knee always ring and break the joint? A slight popping sound will not cause wear and tear on the knee in the short term, but it indicates that you do not have enough synovial fluid in the joint cavity. In the future, it is best to do some preparatory activities before exercising, and then do formal exercise after a full warm-up. For people with inward and outward patellar displacement, it is best to master the correct exercise method and try to avoid squatting, climbing stairs and other exercises. The ordinary physiological popping will not “wear out” the knee joint.