Cartilage injuries can occur at the padding between joints or at the surface of the bones at the joint. When people refer to an injury as "torn cartilage," they are most likely referring to the cartilaginous padding between the joints. On the other hand, cartilage injury due to wear and tear or arthritis are usually associated with the articular cartilage which lines the surface of the bones at the joint.

Cartilage injuries are most common at the knee, hip, shoulder, and elbow.

Further Reading:

American Academy of Orthopaedic Surgeons: Articular Cartilage Restoration