The following causes are common: First, congenital joint laxity, the joint in the development process, the surrounding ligaments and joint capsule is too loose, which will lead to joint instability, so when walking easily appear joint clacking, especially if the patient is overweight, the sound will be more obvious, through physical examination can confirm joint laxity. Second, joint wear and tear produces degenerative osteoarthritis, with the age of the whole body, many joints will undergo significant degenerative changes, the joint surface cartilage appears serious wear and tear, manifested as uneven joint surface, and joint rattling when walking, most of the middle-aged and elderly patients, through the MRI examination can be found in the joint cartilage large area of damage. The majority of patients are middle-aged and elderly.