Knee cartilage reconstruction. Artwork showing the second stages of a method to reconstruct the cartilage in a damaged knee joint. Here, new chondrocytes (cartilage cells) have been cultured and are being injected into the damaged area (expanded illustration at right). To seal the new cells in place, a circular flap of tissue from the tibia has been sewn over the area to be treated. The injection is done through the seal. This procedure is done for conditions such as osteoarthritis. For the first stages of this process, known as autologous chondrocyte implantation, see image C007/24610.