Microfracturing is a biological method that can be carried out arthroscopically. The surgeon creates tiny fractures in the bone underlying the damaged cartilage surface (the subchondral bone plate). Blood and bone marrow, containing stem cells, seep out of the fractures, creating a blood clot that promotes the growth of cells and builds cartilage-like tissue referred to as fibrocartilage (scar tissue), that has lower durability than natural articular hyaline cartilage. This treatment is not optimal for older patients or cartilage lesions larger than 1.5 cm in diameter. Results further tend to deteriorate with time.