Epifluorescent micrographs of stained chondrocyte nuclei (white dots after imaging processing) within human femoral head articular cartilage, when subjected to graded levels (8, 17, 25, and 31%) of equilibrium-confined compression. Arrows and circles indicate tracking of cell nuclei. (Reproduced from Osteoarthritis Cartilage, 9, S. S. Chen, Y. H. Falcovitz, R. Schneiderman, A. Maroudas, R. L. Sah, Depth-dependent compressive properties of normal aged human femoral head articular cartilage: relationship to fixed charge density, 561–569, Copyright 2001 with permission from Elsevier.)