OARSI 2026: Osteoarthritis's 'non-inflammatory' label is cracking
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Even in cases where the arthritis is considered well-managed, a persistent state of low-grade inflammation can still be present. Recognizing this shift in understanding is crucial because it means treating OA isn't just about structural repair, but also long-term inflammatory control.
—Harpreet Bawa, MD
The ‘non-inflammatory’ label was always a teaching shortcut, and one we should probably retire. Anyone who has operated on a knee has seen synovitis. The effusions (swelling) are real. Calling it ‘non-inflammatory’ because it does not fit with the RA phenotype does not serve us well.
—Cory Calendine, MD
Osteoarthritis (OA) has generally been classified as a non-inflammatory arthritis, but the long-standing assumption was recently challenged by new research presented at the Osteoarthritis Research Society International's 2026 World Congress on Osteoarthritis (OARSI), held April 23-26 in West Palm Beach, FL.[]
“Evolving evidence in orthopedics is increasingly showing that OA is not simply cartilage getting old,” Stephen. Stache, Jr, MD, FAMSSM, a non-operative sports medicine physician, tells MDLinx. “Many patients demonstrate low-grade chronic inflammation involving the synovium [joint lining]), bone below the joint lining, and joint-protecting fat pads.”
Challenging assumptions
Several research abstracts presented at OARSI 2026 support this new understanding. Consider the following:
The mechanisms of synovial inflammation, specifically, atypical activation of the protein BRD4 within the OA synovium: BRD4 stimulates CD169 macrophages, which enhances glycolytic metabolism and promotes the secretion of chemokines and inflammatory cytokines. These actions, plus others, intensify the synovial inflammatory cascades. Targeting BRD4 activity in CD169 tissue-resident macrophages might therefore offer a promising therapeutic strategy for slowing OA progression.[]
Metabolic dysregulation of fibroblast-like synoviocytes (FLS) plays a role in OA pathogenesis: The KDM4A/FTO/m6A/ESM1 signaling axis critically regulates FLS energy metabolism, affecting the glycolysis/oxidative phosphorylation balance, thereby restraining synovial fibroinflammation and OA progression. This study identified FTO regulation as a possible option in treating OA.[]
Chronic inflammation is a potent driver of OA progression: The research also considered peptides as a potential therapeutic option.[]
Expert takeaways on inflammation in OA
Harpreet Bawa, MD, an orthopedic surgeon and joint replacement specialist, offers some insight on OA inflammation. “The intensity of inflammation associated with osteoarthritis is highly variable; it fluctuates based on the disease’s severity and the effectiveness of the treatment plan,” he says. “Even in cases where the arthritis is considered well-managed, a persistent state of low-grade inflammation can still be present. Recognizing this shift in understanding is crucial because it means treating OA isn't just about structural repair, but also long-term inflammatory control.”
Dr. Stache adds that OA inflammation isn’t auto-inflammatory in nature. “This inflammation is not the same as rheumatoid arthritis, which is an autoimmune inflammatory disease, or the body attacking itself,” he notes.
Cory Calendine, MD, an orthopedic surgeon, agrees wholeheartedly. “The ‘non-inflammatory’ label was always a teaching shortcut, and one we should probably retire. Anyone who has operated on a knee has seen synovitis. The effusions [swelling] are real. Calling it ‘non-inflammatory’ because it does not fit with the RA phenotype does not serve us well.”
Dr. Calandine also notes GLP-1 therapy’s beneficial effect on OA. “That it goes beyond weight loss alone tells us OA is not just a mechanical problem,” he says.
“I would explain it like this: OA can be mechanically initiated in many cases, but inflammation is the core driver of progression and life-changing symptoms. This frame will allow us to consider treatment options beyond the cartilage wear model,” Dr. Calandine says.
Raquelle Felder, DPT, owner and founder at San Diego Mobile Rehab and Physical Therapy, agrees. “I'm happy to see that we are gaining more understanding of OA,” she said. “This is actually encouraging, since we may be able to have more control of the amount of inflammation in our body with diet and healthy lifestyle habits. Although it can't prevent or cure OA, lifestyle changes could improve the inflammation component of OA.”