Articular cartilage is an excellent bearing material able to withstand high loading pressures and experience little wear for nearly 70 to 80 years. Many investigators have suggested that these remarkable properties stem partly from the pressurization of cartilage interstitial fluid during joint loading (e.g., [1,8]). Indeed, theoretical analyses of biphasic or poroelastic cartilage contact have demonstrated that upward of 90% of the contact load may be supported by interstitial fluid pressurization (e.g., [1,6,7]). However, direct experimental verification of these theoretical findings has been difficult to achieve and few studies have reported direct measurements of cartilage interstitial fluid pressure [2,3]. Thus, the objectives of this study are to measure both the fluid pressure and total load acting at the cartilage contact interface, to determine the fraction of load supported by interstitial fluid pressurization as a function of time [3], and to compare this result with the biphasic theory for cartilage [9]. These objectives are achieved by testing cartilage cylindrical plugs under confined compression stress-relaxation.

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