Histological examination of knee joint meniscectomy specimens revealed previously undescribed basophilic spindle shaped structures. This study was done to explore their structure, to discuss potential mechanisms for their development and to establish diagnostic criteria. --4000 surgical specimens were examined. The intercellular substance of the cartilage was studied by means of mucopolysaccharide histochemical and polarisation optical methods. The three-dimensional fiber construction was examined stereometrically by means of a procedure derived from the universal stage method of the mineralogists. The spindle-shaped structures seem to be a sign of reduced mechanical tissue resistance. They are performed but become visible during meniscal degeneration. The mechanically efficient element of the menisci is a triple dimensional network of collagen fibers. Longitudinal fibers assure the tension resistance of the tissue. Transverse and diagonal fiber bundles tie the longitudinal fibers together. They act as tension rods. Therefore, compression resistance results. Meniscal degeneration mainly takes place in the tension rod fibers. Therefore, degenerated menisci tend to burst longitudinally. The condition of tension rod fibers in important as an indicator of mechanical resistance of the cartilage. It is a parameter for the assessment of meniscal damage.