Synovial fluid chondroitin sulphate indicates abnormal joint metabolism in asymptomatic osteochondritic horses.

The research investigates the effects of osteochondrosis dissecans (OCD) on the composition of synovial fluid in horses and suggests that measurements of chondroitin sulphate and white blood cell count could act as indicators of joint health and disease progression.

Research Objective and Methodology

• The objective of the study was to investigate possible changes in the composition of synovial fluid— the fluid that lubricates joints— that may indicate joint conditions in horses with asymptomatic OCD, which is a joint disorder in horses that can cause lameness.
• The study involved horses over 2 years of age, of varying breeds, with OCD in the intermediate ridge of their distal tibia (a specific area in the lower leg bone), whether symptomatic or not.
• Synovial fluid samples were collected from 29 horses through a process called arthroscopy. The fluid samples were then analysed for glycosaminoglycans (GAGs), encompassing the likes of hyaluronic acid (HA) and chondroitin sulphate (CS), using a combination of agarose gel electrophoresis and enzymatic degradation.
• The study also took into consideration the viscosity of the fluid, white blood cell (WBC) count, protein concentration, and molecular weight of hyaluronic acid.

Findings and Implications

• The research suggests the method for analysing synovial fluid GAGs is reliable, reproducible, and specific. A majority of the synovial fluid GAGs in normal horses were HA and CS, contributing to 93% and 7% respectively.
• Results showed an increase in both HA and CS concentrations in horses with symptomatic OCD as expressed by the GAG/urea ratio. However, the increase in CS was far more substantial. A similar increase in CS was also observed in asymptomatic OCD horses.
• The study noted that an increase in WBC counts in OCD horses suggests an ongoing inflammatory reaction. Additionally, the molecular weight of synovial fluid HA was found to be reduced in OCD horses, which could explain the observed lower viscosity.
• The findings emphasize that an elevated concentration of CS in the joint fluid of OCD-affected horses indicates that the synovial fluid CS and WBC count serve as notable indicators of joint conditions. This discovery could aid the identification of pathological phases in joint diseases.
• It illustrates that even asymptomatic OCD results in cartilage damage. This damage highlights the need for arthroscopic removal of the osteochondral fragments, even if the horse is currently asymptomatic.