A Joint Barometer

A protein called serum amyloid A (SAA) could help veterinarians assess the condition of a joint before it becomes severe, according to Danish researchers. Joint disease is a major source of lameness in performance horses, and researchers are always striving to identify factors that can give veterinarians an idea of a joint's condition before the disease becomes chronic.

According to Stine Jacobsen, DVM, PhD, of the Department of Large Animal Sciences at the University of Copenhagen's Faculty of Life Sciences in Denmark, one such factor could be SAA.

"These proteins are produced by the organism when inflammation occurs (e.g., in the presence of infections or when the horse suffers a traumatic injury)," noted Jacobsen. "We knew from human medicine that these proteins can be measured in blood as well as in joint fluid, but this had not been investigated in horses. Our idea was that measurements of SAA in joint fluid would provide information about inflammation going on in the joint (high levels of SAA suggest the joint is inflamed or infected)."

Researchers used 10 horses with healthy joints as controls in the study and compared them to 21 horses with a variety of joint diseases. They obtained serum and synovial fluid samples from each horse, and they collected serum samples from five of the control horses nine times to ensure an accurate baseline.

"Synovial fluid SAA concentrations were significantly higher in horses with suspected bacterial joint contamination, infectious arthritis, or tenovaginitis (inflammation of a tendon sheath) than in healthy controls, and serum concentrations were significantly higher in horses with infectious conditions than in the other groups," Jacobsen explained. "Neither serum nor synovial fluid SAA concentrations in horses with low-inflammation joint conditions differed significantly from those in healthy controls."

So what does this mean for veterinarians and horse owners?

Jacobsen explained, "At our hospital we now measure SAA on a routine basis. This helps us differentiate between joint infection (which requires immediate intensive therapy such as antibiotics and arthroscopic surgery) and joint contamination (which requires less intensive therapy). This has, thus, enabled us to give better advice to our clients regarding the treatment and prognosis of the joint conditions that their horses suffer from. Moreover, we have seen that SAA levels in joint fluid will decline when joint infections are successfully treated. This has enabled us to better monitor the results of our treatment and to change treatment faster if the horse is not responding to a treatment; this will in turn improve the outcome of the treatment."

Other researchers performing the study were Maj. Halling Thomsen, DVM, and Simone Nanni, DVM. The study was published in the October 2006 issue of American Journal of Veterinary Research, Vol. 67, No. 10, p. 1738.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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