Experimental study and model for healthy and pathological synovial fluid

Abstract

In the present work a comparative rheological study of healthy and pathological synovial fluid (SF)is presented. The SF samples were obtained from healthy dogs or dogs with rupture of cranial cruciate ligament. The rheological measurements were carried out at 25 oC and 38 oC, i.e. at room temperature and at the regular temperature of the dog’s body. A stainless steel rotating disk of 20 mm diameter was used on the rheometer AR-G2 and the gap between the plate and the disk was up to 125 μm. It was found that for the healthy SF, the viscosity was reduced by three orders of magnitude (from 40 Pa·s to 0.04 Pa·s) as γ(dot) was increased from 10-3 up to 800 s-1. For the pathological cases and for the same range of shear rates the viscosity values were between 1 Pa·s and 10-2 Pa·s. An established rheological model, i.e. the Carreau model, was used to describe the flow curves with successful results. Finally, the viscoelastic behavior was recorded by oscillatory and creep measurements and the obtained results indicate that the retardation time increases in consecutive measurements and also that the Cox-Merz rule is applicable in SF rheology.