Chondral is a term used to refer to the gristle or hyaline cartilage at the end of
the bones. When the cartilage is pulled away from the bone it can leave a tiny hole or crater. This is called a chondral defect. The joint surface is disrupted and no longer smooth at the point of injury.
When the cartilage pulls away from the bone it can take a piece of the bone with it. That piece of bone is a loose body, sometimes called a knee mouse.
Cartilage can't repair itself, and these types of injuries can lead to arthritis. Early treatment to remove the loose body and repair the joint surface is often advised.