Figure 2: Overview plate of the defects in the trochlear ridge of the distal femur treated with A-E: a single layer (hyaluronan web), F-J: double layer (hyaluronan web & collagen type I/III fleece) of transplants, and K-O an untreated defect as control. The macroscopic overview images show A: a well-filled defect containing whitish tissue, F: a defect with translucent tissue and reddish appearance due to the underlying bone in the transplanted defects, and K: only local tissue in the control. The squares indicate the areas from which the tissue sections in B, G and L were taken. B, G and L: In those sections the complete filling (B) and incomplete filling (G, L) are visible. The dotted line indicates the interface between RT and NC. Only in the control does the RT not adhere well to the calcified cartilage (arrow). In the single transplanted defect C: toluidine blue staining and D: immunohistochemistry against collagen type II (brown staining) show hyaline-like tissue (under the dotted line) similar to NC. In the double transplanted defect and the non-transplanted control, H, I and M, N the whole RT is pale with little toluidine blue staining (H, M) and not positive for the collagen type II reaction (I, N). E, J and O: TEM images demonstrating the different structure of matrix and cells. In the hyaline tissue (E), the matrix is homogeneous and only few fibres are visible extending upwards to the joint surface (arrow). The fibres appear bright in the generally grey matrix. In the fibrous tissue of the double transplanted defect (J) and the control (O), the matrix is very fibrous and the cells polygonal. In the control the cells are extremely irregular and dark. Scale bars: (B, G and L) 1 mm, (C, D, H, I, M and N) 250 µm, (E, O) 10 µm, (J) 5µm.