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[Characteristics of Focal Degenerative Cartilage Lesions in the Knee Joint. A Radiologic, Spectroscopic, Histological and Biochemical Study].

OBJECTIVE
The aim of this study was to perform a macroscopic, spectroscopic and biochemical/histological examination of the defect margins of grade IIIb cartilage lesions in the patella, the medial femoral condyle, the corresponding articular surface and the remaining cartilage surfaces of the knee joint. Our null hypothesis was that there would be no difference in characteristics between the cartilage surrounding the defect, the corresponding articular surface and the remaining articular surfaces of the knee joint on the one hand and the cartilage within the defect on the other.


METHOD
The study included ten patients treated for focal cartilage lesions (ICRS classification grade IIIb) by autologous cartilage transplantation (ACT). All patients underwent a preoperative magnetic resonance imaging scan (1, 5 T). The articular cartilage lesions were classified pursuant to the recommendations of the International Cartilage Repair Society (ICRS). During the arthroscopic procedure, spectroscopic examinations were performed to measure the degree of cartilage degeneration in a total of 14 defined areas including the defect itself and the region of the defect margins. Biopsies for a histological and biochemical examination (collagen II, glycosaminoglycan, DNA) were taken from the centre of the defect and the defect margins that seemed to be intact on macroscopic examination.


RESULTS
All knee joints had focal grade IIIb cartilage lesions with an intact margin and an intact corresponding articular surface. The readings obtained on spectroscopic examination both in the defect, the apparently intact margins, the corresponding articular surface and all other examined areas of the knee suggested that severe degenerative changes had already occurred in the cartilage. The histological and biochemical examinations of the residual cartilage in the centre of the defect and the apparently intact margins revealed no significant differences.


CONCLUSIONS
Focal cartilage lesions frequently occur in the main weight-bearing zones of the patella and the medial femoral condyle. If they are the result of degenerative changes in the knee joint, the residual cartilage in the defect does not differ from the cartilage of the defect margins, the corresponding articular surface and the other cartilage surfaces. This leads to the conclusion that focal cartilage defects seen in degenerative joint damage are only one aspect of general joint degeneration.