Hyaluronic Acid HA is a polymer found in synovial fluid. HA has viscoelastic properties. HA acts as a lubricant and a shock absorber.

Synovial Fluid Synovial Fluid is found in joints. It acts to lubricate and absorb shock in the joints. This fluid is contained in the synovial cavity. Hyaluronic Acid (HA) is a polymer found in synovial fluid, giving the fluid its viscoelastic properties. Legend® is a commercial product containing 10.0 mL/mg HA and is used to treat lameness in horses.

Objective To discover how adding Legend® to a horse’s synovial fluid affects its viscoelastic properties.

Basic Procedure We wanted to find the effects of Legend® in three different samples of synovial fluid: a five day-old foal, a horse older than twenty, and a normal horse. We began by testing pure synovial fluid samples on a rheometer. This way we could see any changes that would occur after we added the Legend®.

Vocabulary Rheology: the study of the deformation of materials. Rheometer: Measures the deformation of materials. G’ modulus: represents the elastic properties of the liquid in a dynamic test. G” modulus: represents the viscous properties of the liquid in a dynamic test. Cross-over point: the point at which G’ and G” intersect. This is where the dominant property changes from elastic to viscous or vice versa. Viscosity: a liquid’s resistance to flow. Elasticity: the property of returning to an initial form or state following deformation

Dynamic Testing The rheometer oscillates the bottom plate against a 1º cone causing deformation in the sample. This test measures the elastic and viscous moduli. When the graph shows the G” modulus above the G’ modulus, the fluid has more dominant viscous characteristics. When this is reversed, the fluid’s elastic properties are more dominant.

Steady State Testing Under steady state testing, the rheometer performs several tests at increasing rates. By spinning the plate against the cone in one direction, the viscosity of the synovial fluid is measured.

Testing first under a dynamic frequency sweep test and then a steady rate sweep test, we measured the viscoelastic properties of the different synovial fluids. Next we tested a mixture of 30% Legend® and 70% synovial fluid by volume. We wanted to see how adding the Legend® altered the properties of the synovial fluid.

Conclusion We found that adding Legend® to the synovial fluid increases viscosity and elasticity. Adding Legend® affected the two samples differently. We suspect that the discrepancies are due to the variations in age and conditions of the joint.