Why can bone injuries heal much more rapidly than injuries to cartilage?

Rich blood supply: Because of the lack of blood supply to cartilage, (a new technique to hasten healing of injuries is to introduce fresh blood flow into the area) whereas the marrow in bones actually produce red blood cells, and bones are actually a honeycomb like structure, and they are constantly being taken apart, and rebuilt, microscopic bit by bit.

Blood supply: Bone has good blood supply. Cartilage relies on either synovial fluid or subchondral bone. Very difficult to get cartilage lesions to heal.