New patients with cartilage loss

In today's clinic, I had the chance to see two young patients- both in their twenties, with painful knees due to loss of cartilage. the first had a "hole" affecting the inside of the knee, about 4 sq. centimeters, which is large. We are going to grow some cartilage cells from the patient's body, expand them in culture, and the replace them in the knee. They will then stick to the hole and grow.
The second patient had a similar problem but affecting the back of the kneecap. Unbelieveable, the insurance company refuse to pay for the surgery because this location was not tested when the product went through trials. This is just a lame excuse. So as an option, I am going to take some cartilage from a tissue bank and see if a good repair can be made. More on the hazards of tissue banking later.