The surface of human menisci and its aging alterations during age. A combined scanning and transmission electron microscopic examination (SEM, TEM).

Eight macroscopically normal menisci of different ages were obtained at autopsy to study their surface structure. The investigation was carried out using transmission and scanning electron microscopic (TEM, SEM) examinations. The combined methods have not been used before. An understanding of physiologic alterations during age has to be furnished for further research of pathological alterations. The surface relief shows clear differences in different age groups. The meniscus surface of the newborn is built of randomly arranged, equally sized folds and cell formations. The TEM-examination reveals a loose net work of collagen fibrils which is not covered by a membrane-like structure on the joint cavity surface. With age the linear folds become wider extending from the anterior to the posterior segment. They are most prominent in the inner zone; in the middle and outer zone they are flattened at areas of interdigitation. These folds are most likely preparation artefacts rather than closely packed fiber bundles or pathologic osteoarthritic alteration of the surface. This is supported by the TEM examination showing a loose 3-dimensional fiber net work. Early degenerative alterations of the meniscus surface are characterized by a slit-like destruction of this superficial fiber net.