Viscosity of equine synovial fluid.

This study investigates how the viscosity, or thickness, of synovial fluid in horse joints changes under different conditions, such as in the presence of inflammation or infection. This is measured using a device called a Rotovisco RV3 rotational viscosimeter.

Study Design and Methodology

• The researchers looked at synovial fluid samples taken from 51 light horses.
• The samples were taken from different joints including the carpal (the equivalent of the human wrist), stifle (the equivalent of the human knee) and hock (the equivalent of the human ankle).
• The joints from which the samples were taken were both healthy joints, and joints affected by synovitis (inflammation of the joint) or infectious arthritis.
• The properties of the synovial fluid were studied using a Rotovisco RV3 rotational viscosimeter, a machine that measures the resistance of a fluid to flow.

Findings of the Study

• The researchers found that synovial fluid from both healthy and diseased joints exhibited complex rheological properties. Rheology is the study of the flow of matter: in this case, how the fluid changes when a force is applied to it.
• Most samples exhibited variable viscosity: that is, the thickness of the fluid changed with the rate of shear, or the speed at which force was applied to it.
• One exception to this was the synovial fluid taken from joints with infectious arthritis. This fluid appeared to react differently, although it is not specified how in this abstract.

Conclusions of the Study

• Instead of single observations on viscosity, the researchers considered that flow curves – graphs showing how the fluid’s behavior changes with different shear rates – were a more accurate representation of the properties of the synovial fluid.
• This suggests that synovial fluid may respond differently under varying conditions, and that this versatility may have implications for how diseases affecting horse joints are diagnosed and treated.