Some people consider this a "design flaw" in the human body. Cartilage anywhere in the body doesn't have a big blood supply. We say it's not highly vascularized. This means when it's injured or damaged in anyway it heals very slowly or not at all.
The cartilage doesn't have a way to heal itself. The result is often worse symptoms for the patient and joint degeneration. Surgery is done to repair the damage and bring blood to the area to speed up the healing cycle.
Cartilage has several layers. The deepest layer just before the bone is called the tide mark. Just below the tide mark layer are stem cells that can grow into fibrocartilage. This kind of cartilage isn't exactly the same as the cartilage on the surface of the joint, but it's better than nothing!