Knee rattling, but no pain symptoms, commonly due to chronic injury to the knee joint, knee meniscal laxity, etc., as follows: First, chronic injury to the knee joint: usually occurs in excessive exercise or elderly patients, the patient will have mild cartilage wear, cartilage wear will produce joint surface unevenness, the patient will have obvious joint rattling, but early no pain symptoms, only extensive damage Only a large area of damage will cause significant pain and limited movement. MRI can reveal mild cartilage damage. Second, knee meniscus laxity: the meniscus and joint capsule joint laxity, walking or movement will appear joint ringing, mainly due to the meniscus out of the original anatomical position, but the patient does not have pain, until the meniscus tears will cause knee joint pain.