Introduction: Osteoarthritis (OA) is the most prevalent joint pathology worldwide. OA is the leading cause of disability among older individuals. The medical and societal burden of OA makes the understanding of its pathogenesis and potential treatments paramount. Objectives: This narrative review seeks to explore the most up-to-date literature regarding the M1 - M2 macrophage transition that has been proposed as the possible solution for the pathogenesis of OA. Methods: PubMed was queried for “macrophages and the pathogenesis of OA”, as well as “M1 to M2 transition in OA”. Articles were included in our review if they focused primarily on the role of macrophages in OA pathogenesis and the specific role the M1 to M2 macrophage transition has in the development and resolution of osteoarthritis. We focused on key examples where the M1 - M2 transition could be exploited in the resolution of OA. Results: Aberrances in the physiologic M1 - M2 macrophage transition can promote the pathogenesis of osteoarthritis and a degenerative state. When there is a predilection for M1 proinflammatory macrophages in the joint, progression to OA may result. Conversely, when there is a predilection for M2 macrophages in the joint, OA is typically absent, and the induction of an M2 predominant state may alleviate symptoms and further joint destruction of OA. Conclusion: The M1 - M2 macrophage transition plays a key role in the pathogenesis and severity of OA. Exploiting biochemical pathways involved in this transition may prove to be a suitable treatment for patients with OA.
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