Checking ball joints involves identification of any abnormal rattling, bumping or scraping from the front end and location of the ball joint under the steering knuckle. Identify if it is the rubber, the joint or the metal friction problem. Test the steering and suspension to know if it needs replacement.
Listen to the vehicle while driving if it makes any noise on the front end. Check the vehicle using the control arm or the strut arm suspension. Using the control arm, check for any wear indicator at the ball joint under the steering knuckle while it is still on the ground. If the boss recedes into the housing, there is a grease fitting or the rubber boots are not in one piece, are torn or gone, it needs to be replaced. Ensure no rust dust that would be causing friction.
Raise the front end of the car to release tension and ease play on the joint. Secure the car on the stands and rock the wheels to check for play. If it is in good condition, there should be no play. Turning the wheel side to side gives feel for any excessive or choppy movement. Pushing and pulling of the road wheels will detect any give. If it moves around too much, it needs to be replaced.