The common causes of knee creaking are physiological popping, osteoarthritis, meniscus injury and so on. 1. Physiological popping: the knee joint contains joint fluid and a certain amount of gas, when moving the knee joint, due to pressure and extrusion, the gas will be discharged sound. 2. Osteoarthritis: Due to the reduction of joint fluid and damage to the cartilage, friction occurs between the cartilage when the knee joint is moved, and a sound will be heard when the knee is straightened. 3. Meniscus injury: the meniscus is squeezed and damaged during exercise and knee bending, and a popping sound is made when the knee is straightened because the ruptured meniscus is squeezed by the pressure. Caused by the knee straightening creaking, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor for standardized treatment.