Rattling of the joints during flexion and extension is a physiologic reaction if it is occasional and not accompanied by any pain or dysfunction. If there is frequent popping of the joints, it is necessary to consider the existence of joint diseases, common arthritis, joint hyperplasia and degeneration, damage and wear of articular cartilage, and inflammatory hyperplasia and hypertrophy of ligaments around the joints, including synovitis, which will lead to friction and collision between the bone and the bone, between the bone and the surrounding soft tissues, or between the articular cartilage when the joints are moving, and thus the symptoms of popping will appear. Symptoms. If it occurs frequently, there must be a pathological basis that causes deformation and mismatch of the joints, which leads to friction and impact sound. Therefore, if there are frequent sounds when flexing and extending the joints, there must be a cause of the disease, and it is recommended to go to the hospital for examination.