Concentrations of keratan sulfate in plasma and synovial fluid from clinically normal horses and horses with joint disease

OBJECTIVE: To determine whether keratan sulfate concentrations in plasma or synovial fluid from clinically normal horses were different from concentrations in horses with joint disease and whether concentrations varied with type of joint disease. DESIGN: Case-control study. ANIMALS: 67 clinically normal horses, 10 clinically normal foals, and 160 horses with joint disease. PROCEDURE: ELISA was used to measure keratan sulfate concentrations. RESULTS: Mean plasma keratan sulfate concentration (mean +/- SEM, 580 +/- 124 ng/ml) in foals peaked at 10 weeks of age. Mean plasma keratan sulfate concentration in clinically normal horses was 200 ng/ml (95% confidence interval, 157 to 251 ng/ml). Horses with osteochondral (chip) fractures, other closed intraarticular fractures, inflammatory arthritis (synovitis), infectious arthritis, or osteochondrosis had significantly higher plasma keratan sulfate concentrations than did clinically normal horses, but horses with osteoarthritis did not. Breed, gender, and type of joint disease affected keratan sulfate concentration in synovial fluid. Standard-breds with chip fractures of the metacarpophalangeal/ metatarsophalangeal joints had significantly higher keratan sulfate concentrations in synovial fluid than did Thoroughbreds. Keratan sulfate concentrations in synovial fluid from osteoarthritic carpal joints were lower than concentrations in normal carpal joints and tarsocrural joints with inflammatory joint disease. CLINICAL IMPLICATIONS: Keratan sulfate concentration alone was not a specific marker of joint disease but was affected by various joint diseases.