[Treatment of cartilage defects of the knee]

Focal cartilage lesions of the knee joint frequently cause chronic symptoms and therefore require early treatment. Concomitant pathologies such as malalignment, ligamentous instability, or meniscal deficiency have a decisive impact on the outcome of cartilage regenerative procedures and must therefore be addressed concomitantly. Small chondral defects up to approximately 2 cm² are commonly treated primarily by bone marrow stimulation (BMS), preferably using microdrilling techniques. For defects of approximately 1-4 cm², matrix-augmented bone marrow stimulation (m-BMS) is considered the standard of care, providing superior mid-term outcomes. Larger defects exceeding approximately 2 cm² are preferentially treated with matrix-associated autologous chondrocyte transplantation (m-ACT), which has demonstrated stable long-term results. Osteochondral lesions require a combined treatment approach addressing both cartilage and subchondral bone. Overall, treatment follows a clearly defined stepwise concept based on epidemiological factors, defect morphology, concomitant pathologies, and structured rehabilitation.