Hyaluronic acid concentrations in synovial fluid of dogs with different stages of osteoarthritis

To compare hyaluronic acid (HA) concentrations measured in synovial fluid (SF) of joints with different stages of canine secondary osteoarthritis (OA), clinical-orthopedic, radiographic, macroscopic intra-operative and SF findings of 49 joints were assessed. The sum of single findings was correlated to HA concentrations measured by a commercially available ELISA. Joints were categorized into three OA-groups: non-osteoarthritic, mildly osteoarthritic, and severely osteoarthritic. A significant negative correlation was found between severity of OA and HA concentrations (r = −0.696; P < 0.001). Median values of HA concentrations decreased with increasing severity of the disease. Statistically significant differences in HA concentrations were observed between the OA-groups (P < 0.001). Due to overlapping values between groups, it was concluded that synovial HA concentrations may only indicate a trend of osteoarthritic disease activity, but is not suitable for staging the disease.