Ball joint - structure and application. A typical ball joint consists of two cup-shaped stones and a ball pin. The spherical pin can turn in all directions in relation to the stones; it is usually fixed to one and the joined parts, and the stones move in the other. The stones can be pressed with an adjustable spring. Often, however, the joints cannot be dismantled. Usually, due to their nature of operation, ball joints require good lubrication conditions. The grease supply in the joint is replenished through a grease nipple, usually mounted in the head screwed on the end of the rod. Sometimes in passenger cars, and even trucks, Spherical joints are used with spring elements that work according to the silentbloc principle. Such joints effectively dampen vibrations, impacts and shocks are absorbed by the steering and do not require lubrication.