In ACI, a small sample of healthy cartilage cells is taken from the knee from a part of the joint that receives little stress. These cells are cultured in a laboratory. These cells are then placed during a second surgery. Often at 6 weeks after surgery. Spherox is the name of the drug used to repair the area along with the cartilage. Then the spheres are applied to the cleaned cartilage. The spheres adhere to the cartilage within about 20 minutes. This method is suitable for cartilage defects larger than 2cm2 and brings good long-term results.