@Mor - I saw an episode of Grey's Anatomy recently that dealt with that very topic. There was a girl who had had too many surgeries on the cartilage of her throat and it wasn't able to heal properly.
They used a groundbreaking new technique to "grow" a new piece of thyroid cartilage for her from her own cells and then put it into place with surgery so that she was still able to breath and talk afterwards.
I looked up the procedure because I suspected that they were exaggerating for the show, but they can actually do this with various parts of the body now. Which is great because knee cartilage is one of the things that almost always eventually wears out in the majority of people.