Scanning electron microscopy of normal and rheumatoid articular cartilages.

The fine structure of the surface and superficial layer of the articular cartilage is of special interest for the analysis of the functions and pathological changes of the joint. The arrangement of the collagen fibrils in the surface layer of the articular cartilage has been investigated by the Spaltlinie method (BENNINGHOFF, 1925), by phase contrast microscopy (MACCONAILL, 1951) and by polarization microscopy (MACCONAILL, 1951; TAKEDA, 1968). The transmission electron microscope study by TAKEDA (1968) using replicas seems to be the only work which treats with the fine surface structure of the articular cartilage including rheumatoid changes. WALKER and his co-workers (1969) recently demonstrated the surface view of the articular cartilage by scanning electron microscopy. Although they described the occurrence of bundles of collagen fibrils and of spherical particles which they presumed to represent an "acid-protain complex of spherical configuration," their electron micrographs seem not very adequate for a detailed analysis of the surface structures of the cartilage presumably because of an inappropriate method of specimen preparation. The scanning electron micrographs of the articular surface included in the preliminary report by MACCALL (1968) do not seem to clarify the detailed structure either. The present authors who recently reported on the normal aspect and the rheumatoid changes in the surface of the synovial membranes under the scanning electron microscope (FUJITA, INOUE and KODAMA, 1968), attempt in this paper to extend their observation to the surface structure of the articular cartilage which is known to be greatly damaged during the early stage of rheumatoid arthritis.