10/28/2025
Does the gut microbiome have anything to do with osteoarthritis (OA) in dogs? OA (often referred to as degenerative joint disease or DJD) has traditionally been considered a localized disease process involving cartilage degeneration, synovial inflammation, and progressive damage to supportive structures such as tendons and ligaments. Though still not completely understood, factors such as age, genetics, activity level, obesity and diet have been associated with the development and progression of OA. In most cases, OA is secondary to some mechanical abnormality such as elbow or hip dysplasia or ligamentous damage (e.g., cranial cruciate ligament injury). Over time, joints afflicted by OA are characterized by increasing levels of inflammatory mediators and damaging enzymes which act in concert to perpetuate joint damage. As OA progresses, periarticular bone forms (osteophytes) and synovial fluid volume increases (joint effusion). Because OA is over-represented in the senior population, the effect of mechanical “wear and tear” of joints over time has been regarded as a major factor in OA progression. OA affects about 25% of all adult dogs and is closer to 80% in older adult dogs. Are the progressive inflammatory and destructive processes involved in OA progression confined to the joint, or could there be systemic factors at play? There is increasing evidence in recent years that the gut microbiome plays a major role in the pathophysiology of OA, an interaction sometimes referred to as the “gut-joint axis”. If you want a quick review of dysbiosis and how it affects the integrity of the intestinal barrier, look at my “Poop for thought” paper (doi:10.5455/OVJ.2025.v15.i2.6). The same inflammatory mediators and harmful bacteria (and their products, like LPS) that breach the intestinal barrier that lead to CNS problems can also reach synovial joints. Dysbiosis, including periodontal disease, has been implicated in the progression of OA in rodent models and humans. Although generally considered sterile, some studies in humans have identified bacterial RNA and DNA in the synovial fluid and cartilage of OA patients. While some of these findings may represent contaminants, there is speculation that there may be a normal (and abnormal) joint microbiome. The first figure (Sun C, et al. Front Immunol 2023) gives a brief description of the effect of dysbiosis on OA. The second (Sun N, et al. Front Cell Infect Microbiol 2025) provides a schematic of potential dysbiosis-directed treatment strategies. What does all this mean? From one perspective, it means we may have a lot more to worry about when dealing with progressive OA in dogs. From a more optimistic perspective, it means we may have an entirely new and mainly unexplored treatment arm for canine OA patients.
