Radiography’s ability to correctly identify joints without OA was 97%, meaning it had few false-positives, and that radiography was equal to or better than MRI for detecting early joint changes consistent with OA.

Photo: Kevin Thompson/The Horse

Osteoarthritis (OA) is a progressive deterioration of joint health with no known cure. Not only does OA negatively affect athleticism and quality of life but it is also a major cause of economic loss throughout the equine industry.

For years researchers have been trying to find ways to diagnose OA early in the course of disease to either slow or, better yet, arrest its progression. And although OA has proven a stubborn opponent, an international group of researchers recently found that radiographs (X rays) and low-field MRI appear to be useful tools for diagnosing OA.

“For our study we chose to use Icelandic horses, a breed that is known to have a high prevalence of OA and one in which a large number of older riding horses are culled due to the pain and lameness that result from the disease,” explained Charles Ley, BVSc, Dipl. ECVDI, PhD, from the Swedish University of Agricultural Sciences, in Uppsala. “Young horses without obvious lameness were used in the study in order to include horses likely to have a very early stage of the disease and normal horses. We chose to use two noninvasive and clinically available imaging techniques—radiography and MRI—to see if it was possible to detect early OA changes in the joints.”

Ley and colleagues collected 75 hock joint radiographs and MRIs from 38 Icelandic horses between the ages of 27 and 31 months. The team then used microscopy to classify joints as positive or negative for OA.

The team classified 42 of the 75 joints as OA-positive after they detected lesions on both radiography and MRI that corresponded with OA, including mineralization front defects and joint margin lesions. The team determined that radiography’s ability to correctly identify joints without OA was 97%, meaning it had few false-positives, and that radiography was equal to or better than MRI for detecting early joint changes consistent with OA.

“Radiography is a widely available, cost-effective, and repeatable method, and the high specificity and high frequency of the detection of mineralization front defects in radiographs suggests that this is a promising marker of early OA in the distal intertarsal joint (one of the middle hock joints),” Ley concluded. “Such a tool has a vital role in selecting horses for inclusion in long-term studies of how and why OA develops and evaluating early intervention and prevention methods for OA.”

The study, “Detection of early osteoarthritis in the centrodistal joints of Icelandic horses: evaluation of radiography and low-field magnetic resonance imaging,” will appear in an upcoming issue of the Equine Veterinary Journal.