Stretching the knee with a ringing sound without pain may be caused by the lateral discoid meniscus, joint tissue lesions, gluteal myofascial contracture and other reasons. 1. Lateral discoid meniscus: the lateral meniscus should normally be crescent-shaped, crescent-shaped, if the patient has a discoid meniscus, i.e., the meniscus is disc-shaped and the medial side is larger and thicker, the medial joints will pop when the patient flexes the knee, but often there is no pain. 2. Joint tissue lesions: may be due to a variety of reasons caused by the presence of synovial folds between the patellofemoral joints increased, thickening, the patient squats the patellofemoral joints will appear up and down bouncing and accompanied by popping, and sometimes with the hand can be touched, and part of the patient can be painless. 3. gluteal myofascial contracture: in patients squatting due to the lateral iliotibial bundle is too tight, will lead to popping around the knee joint without pain, may also be in the middle of the big thick rumble popping and mistakenly thought to be the lateral knee popping. Stretching the knee ringing without pain can also be seen in other causes, it is recommended to go to the hospital in time, do the relevant examination to clarify the cause of the disease, follow the doctor’s instructions for treatment.