Microfracture is a cartilage reparative technique that stimulates the bone marrow. If you have a full thickness defect in the articular cartilage which exposes the underlying bone and is not greater than 1.5 cm x 1.5 cm in size then this may be an option for joint restoration. Multiple holes are punched through the bone which encourages blood and stem cells to fill in the defect. This creates a blood clot which heals the defect with fibrous cartilage.
There are newer adaptations to this technique which are interesting but somewhat unproven. They include doing the microfracture with a biologic tissue covering called BioGuide. This technique captures the blood clot, prevents it from moving and causes more concentration of the stem cells from the bone marrow. This is called AMIC, Autologous Matrix Induced Chondrogenesis and was designed by the Geistlich Corporation in Germany.
A second adaptation is new from the Arthrex corporation here in the USA. It also does a microfracture as the base procedure, and then places a paste of a-cellular matrix and concentrated blood into the defect. This creates a scaffold upon which the new cartilage is formed leading to a more of a hyaline cartilage (higher grade cartilage) than fibrous cartilage as with microfracture alone.