Osteocalcin in canine joint diseases

Markers of joint disease are much sought after in human and veterinary rheumatology. This study investigated the relationship between markers of bone and cartilage turnover in sera and synovial fluids in naturally occurring canine joint diseases. Osteocalcin (OC) was measured by radioimmunoassay; enzyme-linked immunosorbent assays were used to measure keratan sulphate, chondroitin sulphate, hyaluronan and antibodies to collagen I and II. Dimethylmethylene blue binding assay was used for the estimation of sulphated glycosaminoglycans. Compared to normal dogs significantly higher serum OC was seen in dogs with osteoarthritis (P<0.005), rheumatoid arthritis (RA) (P<0.01) and rupture/stretching of cranial cruciate ligament (P<0.02). Reduced OC was found in RA synovial fluids but this finding is probably of little value as there was too much overlap with normal joint data. Apart from a weak correlation between synovial fluid OC and keratan sulphate, there were generally no correlations between markers of bone and cartilage turnover probably reflecting the lack of any relationship between bone and cartilage metabolism in most canine arthropathies.