A new quantitative method was devised both to establish an objective standard for morphometric diagnosis and to determine the extent of degeneration in osteoarthritic cartilage. Eight normal and forty-eight osteoarthritic humeral heads, subsequently confirmed by light microscopy, were obtained at necropsy. The articular cartilage was observed in situ with a laser scanning confocal microscope (LSCM) and morphometric measurements determined cell density (cells/mm), cell volume fraction (%) and mean cell volume (μm3). The osteoarthritic cartilages were classified according to the following four characteristics: increase in thickness, increase in cell volume fraction, decrease in cell volume fraction, and fibrous pannus. Deviations in cell density and cell volume fraction from normal means were calculated as extent of degeneration. Our present approach aims to provide valuable clues, such as objective stereological information and a unique reference for biochemical and traditional morphological analyses, that clinicians will be able to use in combination with other methods in order to establish a reliable diagnosis.