Healing of chondral injuries depends on the depth and extent of the lesion. A lesion that only penetrates through part of the cartilage's thickness and not through subchondral bone does not have the capacity for self-healing, because of the antiadhesive properties of the cartilage proteoglycans and the absence of access to blood or bone marrow cells. A layer of mesenchymal or synovial cells may cover the edges of such a partial defect when the peripheral proteoglycans are removed, and the defect may eventually fill with fibrous tissue when a scaffold of fibrin clot is inserted and may fill even better if growth factors are added. However, the regenerated tissue does not resemble cartilage, and its mechanical quality has not been reported. Cartilage defects that penetrate subchondral bone, result in spontaneous repair with fibrous or hyaline-like cartilage tissue with inferior structural, chemical, and mechanical properties. Precultivated autologous and allogenic cells, alone or combined with carriers or other types of biological materials, even permanent prostheses, have been used in defects reaching to subchondral bone or penetrating the subchondral bone plate, to improve the quality of spontaneous repair. The repair tissue in these methods ranges from hyaline-like cartilage to fibrous tissue but does not provide normal cartilage morphology, mechanical properties, and durability. The main problems in this method are the wide range of outcomes, the insufficient bond to adjacent cartilage, and the premature degeneration of the repair tissue, which was commonly seen when a method was tested for longer than 6 months. Furthermore, no evidence exists that shows any of the chosen methods to be essentially better than another, and it is still unclear whether any of them is better than simple drilling to bone marrow.