The pair of Isuzu Ball Joints on the lower and upper sections of each spindle makes it possible for the front wheel assembles to change the direction the vehicle will travel down the road. Without the ability of the ball joints to permit the rotation of the wheels horizontally the only path your Isuzu could travel would be straight forward.
The weight of the vehicle is held up by the ball joints on the front end of your vehicle. Because of this they are considered weight bearing components which will require maintenance to keep them in proper working condition. Just like the steering components on your Isuzu, the ball joints require the injection of ball bearing grease at regular intervals to keep them from prematurely wearing.
The typical time interval for the injection of grease into the Isuzu ball joints is during the chassis lube job that is preformed during a routine oil change. To ensure the entire surface of this weight bearing component is covered with grease, the vehicle has to be lifted into the air with the wheels suspended. If this is not done and drive up ramps are used to elevate the vehicle, the entire surface of the joint will not be lubricated causing it to prematurely wear.
The dangers of having worn ball joints on your vehicle are that they will negatively affect the steering ability of the vehicle when the driver needs to maneuver around obstacles. They have also been known to become dislodged from their sockets when the joint is excessively worn causing the wheel assembly to become disengaged from the front end. This could cause your Isuzu to be involved in an accident causing in the loss of control over the direction the vehicle will be traveling in.