A longitudinal incision resembling a bucket-handle tear was made in the menisci of 8 rabbits, 6 dogs, 11 pigs and 12 sheep. In some of the animals of each species the cut was repaired by suturing, and in others it was not. Gross inspection, as well as examination by light and electron microscopy, showed that no healing had occurred after six months in the sutured or the unsutured wounds and that the meniscus was incapable of significant intrinsic repair. In a second experiment longitudinal, transverse and T-shaped cuts were made in the menisci of 12 sheep, and a flap of synovium was sutured into the wound. Three months later there was clear evidence of healing by the formation of cartilaginous tissue. Examination by light and electron microscopy showed that the newly formed repair tissue, possibly derived by metaplasia from the synovium, had a morphology intermediate between hyaline cartilage and fibrocartilage. Synovial implantation may therefore be considered as an alternative to meniscectomy in the management of the torn meniscus.

Amianthoid fibres up to about 1000 nm thick were found in the matrix of a chondrosarcoma. Our findings support the idea that this is a degenerative change and that these fibres are probably formed by coalescence of collagen fibrils.

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Desmosomes or desmosome-like structures do not occur between normal synovial cells but such structures do develop between the synovial cells in cases of traumatic arthritis, rheumatoid arthritis and villonodular synovitis. Morphological evidence is presented suggesting that such structures develop as a result of the interaction of fibrin trapped between synovial cells and the plasmamembrane of these cells.