Tree Peony (Paeonia suffruticosa), specifically its root bark (known as "Moutan Cortex" in Chinese medicine), has been traditionally used in East Asian herbal medicine for the treatment of inflammatory conditions, including arthritis. In recent years, scientific research has provided some validation for these uses, particularly regarding its potential in managing rheumatoid arthritis (RA) symptoms.

The primary active constituents identified are paeonol and paeoniflorin, which have demonstrated anti-inflammatory and immunomodulatory effects. Preclinical studies in animal models of arthritis have shown that extracts of Tree Peony can reduce joint swelling, decrease levels of pro-inflammatory cytokines (such as TNF-α and IL-6), and protect cartilage from degradation. A few small clinical trials and observational studies in China have evaluated combination herbal formulas containing Tree Peony, reporting improvements in pain, swelling, and inflammatory markers in patients with RA.

However, the evidence is not robust: most clinical data comes from studies with small sample sizes, short durations, or the use of multi-herb formulas, making it difficult to isolate the effects of Tree Peony alone. High-quality randomized controlled trials are lacking. Nonetheless, the convergence of traditional use and preliminary scientific data supports moderate evidence for Tree Peony’s use in arthritis, especially as part of integrative or adjunct therapies.