Rheological characterization of an artificial synovial fluid

Rheological measurements on two classes of artificial synovial fluids have been carried out in the attempt to get a suitable but cheap lubricant for wear tests of prosthetic materials. Fluids of both classes are solutions of hyaluronic acid (HA) that, for one class, is dissolved into a simple Ringer solution whereas, for the other class, into a mixture of human serum and Ringer solution. Similar rheological properties have been observed for both classes of fluids. Experimental results have been interpreted by two classical models that are commonly used in the literature to describe the rheological behavior of colloidal systems and of polymer solutions with high entanglement density, respectively. The quality of correlations shows that, at high HA concentrations, entangled structures are largely present and cannot be neglected.