Platelet-rich plasma for the treatment of knee osteoarthritis: an expert opinion and proposal for a novel classification and coding system.

INTRODUCTION: Platelet-rich plasma (PRP) is able to modulate the joint environment by reducing the inflammatory distress and promoting tissue anabolism. Therefore, it has gained increasing popularity among clinicians in the treatment of osteoarthritis (OA), and it is currently proposed beside consolidated options such as viscosupplementation. AREAS COVERED: A systematic review of all available meta-analyses evaluating intra-articular PRP injections in patients affected by knee OA was performed, to understand how this biologic treatment approach compares to the traditional injective therapies available in clinical practice. Moreover, a novel coding system and 'minimum reporting requirements' are proposed to improve future research in this field and promote a better understanding of the mechanisms of action and indications. EXPERT OPINION: The main limitation in the current literature is the extreme variability of PRP products used, with often paucity or even lack of data on the biologic features of PRP, which should not be considered as a simple substance, but rather a 'procedure' requiring accurate reporting of the characteristics of the product but also all preparation and application modalities. This approach will aid in matching the optimal PRP product to specific patient factors, leading to improved outcomes and the elucidation of the cost-effectiveness of this treatment.