The ball joint is a spherical bearing that connects the steering knuckle to the suspension control arm. It serves as the pivot point around which the steering knuckle rotates when the steering wheel is turned, allowing for smooth steering movement. If the ball joint is defective, it can cause noise, vibrations, and unintended movement of the vehicle while driving. In cases where the ball joint is not properly secured, the knuckle and control arm can separate, making normal vehicle operation impossible and potentially leading to accidents. Therefore, quality control is crucial for safety.