Articular cartilage defects in the knee have a poor intrinsic healing capacity and may lead to functional disability and osteoarthritis. Cartilage cell therapy using autologous chondrocyte implantation (ACI) has been established as the first advanced treatment therapy medicinal product. Although this technique has achieved good mid-term results, it is a costly and extensive two-stage procedure which is limited by the number of chondrocytes obtained by biopsy and the dedifferentiation resulting from the expansion phase. Therefore, there is a need for improvement. A new cartilage repair technique should aim at decreasing surgical trauma, lowering complexity, improving logistics and cost-effectiveness while retaining or improving clinical outcome. Direct contact between mesenchymal stromal cells (MSCs) and dedifferentiated articular chondrocytes in vitro showed improvement of the chondrogenic phenotype of dedifferentiated articular chondrocytes. In addition, preserving the pericellular matrix of chondrocytes improves cartilage formation. These chondrons (chondrocytes with their pericellular matrix) have shown improved cartilage formation when combined with allogeneic MSCs in extensive preclinical studies. The cells are mixed with fibrin cell carrier and applied to the cartilage lesion within one surgical procedure. This will reduce patient morbidity and improve patient care through immediate transplantation of a potent cell-based cartilage product. This is a phase I/II prospective monocenter study to evaluate the safety and feasibility of the IMPACT for treatment of focal articular cartilage lesions of the knee.