Abstract
BACKGROUND: The effectiveness of platelet-rich plasma (PRP) injections for knee osteoarthritis and the effects of leukocyte-poor PRP (LP-PRP) versus leukocyte-rich PRP (LR-PRP) are still controversial. PURPOSE: To assess the effectiveness of different PRP injections through a direct and indirect meta-analysis of randomized controlled trials. STUDY DESIGN: Systematic review; Level of evidence, 1. METHODS: A systematic literature search of electronic databases (PubMed, Cochrane Library, and EMBASE) was performed to locate randomized controlled trials published through March 2019 that compared PRP with control treatment. A random-effects meta-analysis was conducted to synthesize the evidence, and meta-regression analyses were conducted to determine the influence of trial characteristics. An indirect comparison was performed to assess the effects of LP-PRP and LR-PRP compared with hyaluronic acid (HA). RESULTS: A total of 21 trials were included. A clinically important benefit for pain relief was seen for intra-articular PRP compared with intra-articular saline (standardized mean difference [SMD] = -1.38 [95% CI, -2.07 to -0.70]; P < .0001; I (2) = 37%) and corticosteroid solution injection (SMD = -2.47 [95% CI, -3.34 to -1.61]; P < .00001; I (2) = 47%). As a result of heterogeneity (I (2) = 89%), there was no conclusive effect compared with HA, even though the pooling effect provided clinically relevant pain relief (SMD = -0.59 [95% CI, -0.97 to -0.21]; P = .003). Indirect meta-analysis showed that there was no significant difference between LR-PRP and LP-PRP. CONCLUSION: PRP injections are beneficial for pain relief and functional improvement in knee osteoarthritis. Larger, randomized high-quality studies are needed to compare the effects of LP-PRP and LR-PRP.