Apparent viscosity of the synovial fluid from mid-carpal, tibiotarsal, and distal interphalangeal joints of horses.

The researchers have compared the apparent viscosity (measurement of a fluid’s resistance to flow) of the synovial fluid (the lubricating fluid in the joints) in three different joints of horses: the mid-carpal, tibiotarsal, and distal interphalangeal joints. They found that the viscosity of this fluid decreased with increased rate of shear (the speed at which the fluid is moving) but found no significant difference between the fluid in each joint. If a decrease in viscosity in the distal interphalangeal joint is noticed, it may be indicative of joint disease.

Study Overview

• The aim of this study was to compare the apparent viscosity of the synovial fluid in three different joints of horses: the mid-carpal, tibiotarsal, and distal interphalangeal joints. This was done to challenge the existing belief that the distal interphalangeal joint holds less viscosity than others.
• Researchers conducted this study using 60 clinically healthy adult horses. They collected the synovial fluid from each of these joints and conducted a viscosity test over a range of shear rates to evaluate its resistance to flow.

Methods & Results

• The viscosity of each sample was tested within a shear rate range of 10 to 250/s, and the apparent viscosity was specifically calculated at multiple intervals: 50, 100, 150, 200, and 250/s.
• The effect of the shear rate on the apparent viscosity was then determined using a two-way ANOVA statistical test, with any significant differences further probed with a Tukey’s test. A significance level of P < 0.05 was applied for these analyses.
• The results demonstrated a phenomenon known as shear thinning behavior in the synovial fluid of all three joints. This means that the apparent viscosity of the fluid decreased as the shear rate increased.
• Importantly, the apparent viscosity of the synovial fluid from all three joints was found not to be significantly different within the shear rate range of 50 to 250/s. This observation challenges the prevailing belief that the distal interphalangeal joint has a lesser viscosity than the other two joints examined.

Conclusions & Implications

• The researchers concluded from their findings that the apparent viscosity of the distal interphalangeal joint is not less than that of other joints, contradicting previous reports.
• This implies that if a decrease in synovial fluid viscosity of the distal interphalangeal joint is observed, it might signal potential joint disease. Therefore, monitoring changes in the apparent viscosity of synovial fluid could potentially be a valuable tool in diagnosing and monitoring joint health in horses.