Chondral or osteochondral lesions are typical injuries in orthopaedics and traumatology. Since there is no regeneration of damaged articular cartilage, these lesions can lead to premature osteoarthritis. Therefore, an adequate therapy for these injuries is an important goal. Nowadays, common methods in cartilage therapy are procedures for the recruitment of mesenchymal stem cells: autologous osteochondral transplantation and autologous chondrocyte transplantation. Currently, autologous osteochondral transplantation is the only procedure that allows the replacement of the defect with hyaline cartilage. However, this procedure has the problem of donor-site morbidity and limited availability of transplants. Stem cell recruiting procedures and autologous chondrocyte transplantation normally achieve a regeneration of the defect with only fibrocartilage tissue, but both can achieve good medium-term clinical results. Each of these therapeutic principles has certain major indications. In order to select an adequate therapy, the classification of chondral or osteochondral lesion is needed. From a multiplicity of classification systems, those of the ICRS are of particular clinical relevance.