Narrator: This is Science Today. Cartilage transplantation is offering young, active patients with damaged knee and ankle joints an alternative to total joint replacement. William Bugbee, a professor of orthopedics at the University of California, San Diego, says they've been using this technique, known as fresh osteochondral allografting, since 1983.

Bugbee: The reason there's been so much interest in this program that we've had for so long is that this is sort of a new frontier in orthopedics - treatment of cartilage lesions. Now, there are different treatments that can be used for smaller lesions in the knee, but the allografting, the actual transplantation is really the best option for people with bigger problems in their knee.

Narrator: Because cartilage has no blood supply, the match is for size only. Once in place, the donor cartilage knits to the patient's own to form a stable bond.

Bugbee: We're operating on people in their teens and twenties. What's going to happen to them when they're forty or fifty? Is this going to prevent them from the inevitable arthritis? That's an unanswered question. But this is the best way to return them to essentially normal functioning during their active years and that's what's so important to them.

Narrator: For Science Today, I'm Larissa Branin.