ULTRASTRUCTURE OF NORMAL AND TORN MENISCI OF THE HUMAN KNEE-JOINT

  • 1 January 1983
    • journal article
    • research article
    • Vol. 136  (JUN) , 773-791
Abstract
Normal human menisci obtained at autopsy (7 cases) and the injured and uninjured portions of torn menisci (nine cases) obtained at surgery were studied with the EM. The surface of menisci is composed of collagen fibrils surmounted by an electron-dense surface coat. Most of the cells in menisci are chondrocytes but a few fibroblasts and cells of an intermediate morphology difficult to classify as either fibroblasts or chondrocytes also occur. Mast cells are found at the vascularized periphery of the meniscus. Myofibroblasts were found in the injured portions of menisci in 3 out of 9 cases studied. A territorial matrix containing fibrils and proteoglycan particles with associated filaments is seen around or adjacent to chondrocytes, but sometimes this matrix is sparse or absent. The interterritorial or general matrix comprises collagen fibrils of widely varying diameters (25-180 nm) set in a sparse interfibrillary matrix containing proteoglycan particles. A few mature elastic fibers and several small or immature elastic fibers and collections of electron-dense filaments are seen in the general matrix. Also seen in this region are calcified bodies and matrical lipidic debris derived by the shedding of cell processes and in situ necrosis of cells. Other features seen in the matrix of the injured portion of the meniscus include: membrane-bound cystic structures; parting and fraying of collagen fibrils; and pools of proteoglycan particles.