We know osteoarthritis (OA) is a painful, degenerative condition that can result in lost training days, poor performance, and early retirement in equine athletes. We also know that there are many different treatments for OA. What we don't know, and what a team of researchers recently investigated, is how certain arthritic joint tissues--such as the subchondral bone (the layer of bone that lies directly underneath the layer of articular cartilage that lines the ends of the bones and lends support to the joint)--respond to treatments such as extracorporeal shock wave therapy (ESWT) and polysulfated glycosaminoglycans (PSGAGs, a common joint therapy).
"Previous studies have shown that both extracorporeal shock wave therapy and intramuscular administration of polysulfated glycosaminoglycans have a beneficial effect in some horses with OA, and these therapies are widely used in equine practice," said Chris Kawcak, DVM, PhD, Dipl. ACVS, professor and equine surgeon at the Gail Holmes Equine Orthopaedic Research Center at Colorado State University.
"The subchondral bone is commonly involved in joint disease and is therefore a potential site of action for ESWT and PSGAGs," relayed Kawcak.
To determine if ESWT or PSGAGs "targeted" the subchondral bone, Kawcak and colleagues created a chip in the middle carpal joint (the lower joint in the knee) in one knee of 24 healthy horses. Three groups of horses were then either treated with ESWT, PSGAGs, or neither. The team evaluated the treatment results by measuring the levels of various markers of cartilage and bone turnover (i.e., synthesis and degradation) in blood and synovial (joint) fluid samples; evaluating bone density; and assessing the structure and composition of the bone.
Key findings of the study were:
- PSGAG had no significant effect on any bone variables; and
- ESWT also did not affect the subchondral bone itself, but increased levels of the bone marker called osteocalcin in the blood were significantly higher in horses treated with ESWT than in the control group.
"Unlike other published studies, we did not find any physical evidence of subchondral bone remodeling, and, thus, healing following either ESWT or PSGAG administration," relayed Kawcak.
However, he noted, serum biomarker changes indicated biochemical evidence of bone remodeling, which reveals evidence of ESWT's efficacy at the biochemical level. These results lend additional support for the use of ESWT in joint disease.
Until further research into a treatment for arthritis is completed, horse owners can work with their veterinarian to manage an OA-affected horse's clinical signs. Some common forms of treatment include oral joint supplements, management with non-steroidal anti-inflammatory drugs, and traditional joint injections.
The study, "Effects of extracorporeal shock wave therapy and polysulfated glycosaminoglycan treatment on subchondral bone, serum biomarkers, and synovial fluid biomarkers in horses with induced osteoarthritis," was published in June 2011 edition of the American Journal of Veterinary Research. The abstract is available online.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.