The operator puts one hand on the joint of the patient, and holds the distal part of the joint with the other hand; when he moves the joint, he may hear or feel friction sound of the joint. A gentle sound of rub of joint may occur in some chronic subacute disorders of joint; and a coarse sound of rub of joint may be heard in bony arthritis. When a joint move to a certain angle, there may appear shrill and tiny snapping sound inside the joint; then it indicates there is dislocated cartilage or corpus liberum.