Morphological patterns of articular cartilage fibrillation.

The morphology of articular cartilage fibrillation is usually studied in sections cut vertical to the surface. The present study instead concerns the appearances seen when the surface is viewed en face. The study has been made on indian ink preparations of unfixed, hydrated tissue mounted in physiological saline and examined by stereomicroscopy at times 10 while in situ on the bone, and by transmitted light microscopy of tangential surface slices at magnifications up to times 150. The results are consistent with an hypothesis that fibrillation represents mechanically induced focal wear of the tissue. Various sorts of "minimal fibrillation" and other types of surface markings are illustrated. The en face pattern of the cartilage lesions is to some extent influenced by anatomical site, and it is suggested that it is modified by the local biomechanical environment and local character of the cartilage. Some, but not all, of the various patterns show orientation in the sense either of being predominantly unidirectional or of having two major alignments one at right-angles to the other. The differing relationships of this orientation, when present, to the direction of joint movement and to the alignment of the superficial collagen and its tensile strength, are described and discussed.