Cartilage repair techniques are the current focus of large amounts of research. Many different strategies have been proposed as solutions for cartilage defects. Surgical techniques currently being studied include: * bone marrow stimulation * osteochondral autograft transplantation * osteochondral allograft transplantation * autologous chondrocyte implantation * cell-based (using chondrocytes or stem-cells) or acellular scaffolding Articular cartilage stem cell paste grafting is another technique in use and is undergoing continued investigation.