A ball joint is is a connection that is flexible. And it allows movement of the two parts of that connection in more than one direction at the same time.
What a ball joint do is really simple. First, they hold the wheel to the car. As you can see in your car, the knuckle that the wheel attached to is supported top and bottom by an upper and lower ball joint. Second, it allows the wheel to turn around and to move up and down. As we’re going down the road the tire hits bumps. We have to have the ability for this suspension system to move up and down.
In modern vehicles, the ball Joint is the pivot between the wheel and the vehicle’s suspension system. Today, we commonly use ball joints in front suspensions and have replaced kingpin/linkpin or kingpin/trunnion arrangement, but we can also find them in rear suspensions of some high-performance vehicles. Ball joints play a key role in the safe operation of vehicle steering and suspension.