The right answer is articular cartilages (bones in general).
A joint, in anatomy, is a junction area between two bone ends, or between a bone and a tooth. A joint is more or less mobile according to its constitution, its form, and the nature of the surrounding elements. Arthrology, or syndesmology, is the part of the anatomy that deals with joints.
Joint cartilage is the connective tissue that covers the friction surfaces of joints. "The articular surface of moving bones is covered with a layer of cartilage that facilitates movement while cushioning shocks.