Green Tea Catechins in Osteoarthritis and Rheumatoid Arthritis: Narrative Review of the Available Literature in the Context of Pathogenesis and Treatment Prospects

Rheumatoid arthritis (RA) and osteoarthritis (OA) are significant global health challenges, fueling the need for innovative therapeutic strategies. Natural polyphenolic compounds, such as green tea catechins, exhibit promising anti-inflammatory, antioxidant, and immunomodulatory properties, making them potential adjuncts to rheumatic disease therapy. This review examines the effects of catechins, particularly epigallocatechin-3-gallate (EGCG), on key pathophysiological processes associated with RA and OA, such as pro-inflammatory cytokine production, oxidative stress, cartilage degradation, angiogenesis, and immune cell activation and proliferation. This study contains experimental data contained in full-text articles published in open-access indexed journals published only in English. The most important conclusions drawn from the in vitro and in vivo studies available so far, as well as studies on patients, show that green tea catechins modulate pro-inflammatory pathways, reduce the level of pro-inflammatory cytokines and improve the condition of the intercellular matrix in joint tissues, limiting the destruction of joint tissues in animals and patients and reducing pain. Although these studies suggest potential benefits, such as reduced inflammation and improved clinical parameters, the number and scale of studies are insufficient to confirm the clinical efficacy in a broad patient population. Therefore, claims of adjunctive therapy to conventional therapies should be interpreted with caution, and further well-designed and more powerful clinical trials are needed to verify the translation of the promising molecular mechanisms of green tea catechins into clinical practice.