The use of platelet-rich plasma in studies with early knee osteoarthritis versus advanced stages of the disease: a systematic review and meta-analysis of 31 randomized clinical trials

Introduction Reports have concluded that platelet-rich plasma (PRP) is an effective and safe biological approach to treating knee osteoarthritis (OA). However, the effectiveness of PRP in advanced stages of the disease is not entirely clear. The purpose of this study was to evaluate whether the use of PRP would be as effective in studies with early-moderate knee OA patients compared to studies including patients with end-stage OA, based on the Kellgren-Lawrence classification. Materials and methods A comprehensive search in MEDLINE, EMBASE, Scopus, and Web of Science databases was conducted to identify randomized controlled trials (RCTs) comparing the effect of PRP injections versus other intra-articular treatments on pain and functionality. A meta-analysis was conducted using a random-effects model and the generic inverse variance method. Results We included 31 clinical trials that reported data of 2705 subjects. Meta-analysis revealed an overall significant improvement of both pain [MD, - 1.05 (95% CI - 1.41 to - 0.68); I-2 = 86%; P <= 0.00001] and function [SMD, - 1.00 (95% CI - 1.33, to - 0.66); I-2 = 94%; P <= 0.00001], favoring PRP. Subanalysis for pain and functional improvement showed a significant pain relief in studies with 1-3 and 1-4 Kellgren-Lawrence OA stages and a significant functional improvement in studies with 1-2, 1-3 and 1-4 knee OA stages, favoring PRP. Conclusion Our results indicate that including patients with advanced knee OA does not seem to affect the outcomes of clinical trials in which the effectiveness of the PRP in knee OA is assessed.