The objective of joint therapy is to decrease pain using an osteoarthritic drug that modifies clinical signs and to minimize further deterioration with a disease-modifying osteoarthritic drug. At the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., David Frisbie, DVM, PhD, Dipl. ACVIM, of Colorado State University's Equine Orthopaedic Research Center, compared the use of polysulfated glycosaminoglycans (PSGAGs) and sodium hyaluronate (HA) in arthritic carpal (knee) joints.

Frisbie urged practitioners to make an accurate diagnosis, assess the clinical severity, and allow an appropriate rest period when implementing a therapeutic plan. Decision for drug therapy must also consider economic limitations and the possible side effects. Currently, there are many therapeutic choices, ranging from non-steroidal anti-inflammatory drugs, corticosteroids, PSGAGs, and HA, to novel biologics such as interleukin-1 receptor antagonist protein (IRAP)--also called autologous conditioned serum (ACS).

Historical studies have demonstrated that either PSGAGs or HA significantly reduce lameness over five to seven weeks following administration of multiple doses. In his presentation Frisbie reviewed treatment using either PSGAGs or HA directly injected into knee joints at two, three, and four weeks following an arthroscopically induced chip fragment in each joint. A control group of horses received saline injections at the same intervals for comparison. The 24 study horses were then exercised five days per week until Day 70. Investigators collected synovial fluid weekly for analysis, along with performing sequential musculoskeletal exams, radiographs, and MRI studies.

Both drugs had beneficial effects on joint-related soft tissue structures, and these effects were somewhat more pronounced with the PSGAGs. The intra-articular PSGAGs appeared to have more potent effects than the intramuscular form. HA provided better benefits of lessened cartilage fibrillation, the initial degenerative changes in osteoarthritis that are marked by softening of the articular cartilage and development of vertical clefts between groups of cartilage cells. There was further support that combining HA with corticosteroids increases therapeutic benefits due to an additional mode of action achieved by steroids that reduces joint inflammation. When a joint is nonresponsive to treatment with corticosteroids, the use of intra-articular PSGAGs is indicated.

In conclusion, Frisbie noted that both intra-articular PSGAGs and HA demonstrate effective clinical sign- and disease-modifying osteoarthritic drug benefits, and they are useful for treating joint injuries, especially those with soft tissue involvement.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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