Ball joints are ball-and-socket joints in the front suspension that serve as the pivot points between the wheels and suspension of your vehicle. On each side, the lower ball joint is pressed into and rests in the lower control arm, while the upper ball joint rests in the upper control arm. Both control arms are hinged to enable the wheel to move vertically. While each ball joint supports a great deal of vehicle weight and works at steadying the wheel, the lower ball joint bears the majority of the vehicle's weight. Consequently, the ball joints are far more likely to wear out. Excessive play in the lower ball joint leads the tire to recover sloppily from a minor jolt, this can be indicated by clunking and/or creaking noises, and odd or extreme tire wear on the front tires.
Vehicles with a MacPherson-strut suspension systems utilize a lower ball joint and an upper strut bearing instead of an upper ball joint. If you have noticed your vehicle wandering or erratic steering or odd tire wear, it could be due to worn ball joints. Ball joints along with other suspension components, should be inspected annually along with a complete wheel alignment. Bring your vehicle in to have it inspected by a qualified service professional.