Infrared Spectroscopy for Detecting Osteoarthritis in Horses

Stepping up their diagnostic game, researchers are using infrared (IR) spectroscopy to screen horses for osteoarthritis. Based on preliminary data, IR spectroscopy can accurately differentiate horses with experimentally induced OA from controls, making this an interesting technique worthy of further study.^*

Osteoarthritis is a prevalent degenerative condition of joints that negatively affects performance and quality of life.

“Being able to diagnose osteoarthritis in the early stages allows us the opportunity to try and slow disease progression and prolong athleticism and patient comfort,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research.

She adds, “Current means of supporting horses’ joints include injectable polysulfated glycosaminoglycan (PSGAG), injectable hyaluronan (HA), and oral supplements containing chondroitin sulfate, glucosamine, hyaluronic acid, and methylsulfonylmethane. Recent work has also shown the benefits of DHA and EPA in reducing joint inflammation.

Scientists studying osteoarthritis look at the disease through various lenses, each hoping to find reliable and accurate ways of identifying joints in the early stages of disease. One such approach is analyzing synovial fluid using “omics” technology, such as proteomics. This involves analyzing the proteins in synovial fluid to determine if certain proteins are over- or underproduced in joints with osteoarthritis compared to healthy joints. The “omics” tests, however, are costly and have so far produced inconsistent results potentially because biomarkers may be intermittently expressed or not proportional to the burden of disease.

A group of veterinary researchers from New Zealand, Hong Kong, Canada, and Colorado State University recently collaborated on a project assessing the ability of IR spectroscopy to differentiate between joints with experimentally induced osteoarthritis and control (healthy) joints. IR spectroscopy is a laboratory technique that analyzes the molecular composition of small volumes of dried synovial fluid, and those molecular structures can be compared between samples.

“This technique does not require the separation of single molecular species associated with disease but instead provides a complex IR signal produced by an array of molecules,” explained the researchers adding that IR can “evaluate a range of known and unknown biomarkers simultaneously.”

IR spectroscopy has previously been studied in horses with osteochondrosis and naturally occurring traumatic arthritis, as well as in dogs and humans. Those preliminary studies show IR spectroscopy has high accuracy, sensitivity, and specificity (measures of how reliable a test is to diagnose the disease), making it a potentially useful diagnostic and screening tool for OA. It is cost-effective, and collecting synovial fluid is minimally invasive.

The research team used the well-established “chip fracture” method of experimentally inducing OA. This is a surgical technique that creates a cartilage and bone fragment emulating a traumatic joint injury. This chip fracture was made in one knee (carpal) joint in nine horses via endoscopic surgery, leaving the contralateral knee joint unoperated (OA control). In addition, eight horses underwent a “sham” operation in which an endoscope was introduced into one knee joint, but no chip was created. The contralateral knee of the sham-operated horses also served as a control (sham control).

Synovial fluid samples were collected immediately before surgery and once weekly for nine weeks. Those samples were then analyzed by IR spectroscopy.

The accuracy for distinguishing between joints with OA and the sham-operated, OA control, and sham control joints was 80%.

“IR spectroscopy accurately discriminates between SF [synovial fluid] in joints with induced OA and controls,” relayed the researchers.

“While this approach can differentiate affected joints from controls with good accuracy in a research setting, it was a short study, lasting only nine weeks using an experimental model. Studies using horses with more advanced osteoarthritis and/or with naturally occurring disease would be helpful. Further, advancements in the IR technique itself are underway using ultra-broadband quantum IR spectroscopy, which holds promise for increasing the sensitivity of the test,” noted Crandell.

Detecting joint changes early in the course of osteoarthritis would allow us to intervene earlier to slow disease progression. Identifying disease-modifying agents of osteoarthritis that can stop the disease in its tracks, or even help the joint tissues heal, would be even more beneficial.

Crandell concluded, “Don’t wait until your horse has signs of osteoarthritis to start supplementing with chondroitin sulfate, glucosamine, or omega-3 fatty acids. Research shows that prophylactic administration of these joint supplements may delay the onset of osteoarthritis. This means that owners could offer joint supplements to young, healthy horses prior to joint trauma or natural wear and tear.”

^*Panizzi, L., M. Vignes, K.E. Dittmer, M.R. Waterland, C.W. Rogers, H. Sano, C.W. McIlwraith, and C.B. Riley. 2024. Infrared spectroscopy of synovial fluid shows accuracy as an early biomarker in an equine model of traumatic osteoarthritis. Animals (Basel) 14(7):986.