Ball joints are spherical bearings that connect the control arms to the steering knuckles. They are used on virtually every automobile made and work similar to the ball-and-socket of human. On modern vehicles, ball joints are the pivot between the wheels and the suspension of an automobile. They are today almost universally used in the front suspension, having replaced the kingpin arrangement. It can also be found in the rear suspension of a few higher performance vehicles. Ball joints play a critical role in the safe operation of an automobile's steering and suspension.