I've of course heard of knee replacement surgery, but I don't think I've ever heard about knee transplants using a knee from a donor. Here's an interesting story about a knee transplant recently performed in Ohio.
"It sounds futuristic, but the knee-transplant surgery that is giving 48-year-old Becky Dougherty a new lease on life has been around for a while.
Because he trained in Toronto, where the procedure originated, Dr.. Peter Brooks of the Cleveland Clinic is one of the few orthopedic surgeons in Ohio doing it."