Intra-articular injections for the management of knee osteoarthritis

Abstract

Osteoarthritis (OA) of the knee is a degenerative disease with complex pathophysiology which affects the whole joint, resulting in pain, stiffness and progressive functional limitation. It presents a significant global socioeconomic health burden and necessitates cost-effective, efficacious and safe solutions. Intra-articular injections of different preparations form a non-operative treatment modality for knee OA, reserved for where conservative measures such as physiotherapy and oral analgesia are insufficient, but where arthroplasty is not yet indicated. Intra-articular injections provide a large concentration of the desired agent directly to the affected tissues, avoiding the side effect profiles of systemic treatments. They can be categorized into non-biologic and biologic therapies, with different treatment protocols. ‘Orthobiologics’ is a relatively new and rapidly evolving area in the treatment of knee OA, targeting specific molecular pathways in the OA pathogenesis. The most common intra-articular injections in clinical practice are corticosteroids, viscosupplementation (hyaluronic acid, HA) and autologous blood products such as platelet-rich plasma (PRP). The efficacy of different preparations remains controversial, with both biologic and non-biologic treatments appearing in professional guidelines for the management of knee OA. Inconsistencies in the guidelines and heterogeneity in study methodology result in an academic field that is potentially difficult to navigate for clinicians, worsened by ambiguous nomenclature and low-quality evidence. The aim of this review is to provide an overview of the most frequently used intra-articular injections for knee OA, focussing on mechanism of action, current evidence and professional recommendations.