Chondrocyte ultrastructure in adult human articular cartilage.

Age changes in the ultrastructure of articular chondrocytes have been studied in detail in mice (Silberberg, Silberberg, and Feir, 1964) and in rabbits (Davies, Barnett, Cochrane, and Palfrey, 1962; Barnett, Cochrane, and Palfrey, 1963). Less has been published concerning the influence of age on cellular ultrastructure in human articular cartilage. This is due partly to the scarcity of suitable juvenile material for comparison, and partly to the difficulty of studying in adults the effects of ageing alone uncomplicated by those of osteoarthritic fibrillation. The present study is based solely on a series of articular cartilages in adult joints, and the results include observations from both fibrillated areas of cartilage and from areas with an intact articular surface. Fibrillation is characterized by a process of fraying and splitting of the cartilage which can lead to its disintegration and erosion; the process is initially localized, involving only focal areas of an affected joint. Many of the lesions are mild and do not cause clinical symptoms. Collins, however, regarded all grades of fibrillation as forms of "osteoarthritic" cartilage change (Collins, 1949; Collins and McElligott, 1960), and this interpretation has been used in the present investigation. The observations here reported are an extension of previous electron microscope studies of human articular cartilage from the adult knee (Collins, Ghadially, and Meachim, 1965; Ghadially, Meachim, and Collins, 1965; Meachim and Roy, 1967; Meachim, 1967). Structures normally present in the cartilage cells are described, and the significance of various changes found in the chondrocytes is discussed in relation to ageing and to osteoarthritis.