title: Efficacy of platelet-rich plasma injections in osteoarthritis of the knee: a systematic review and meta-analysis.
abstract: BACKGROUND
  The effectiveness of platelet-rich plasma (PRP) injections for osteoarthritis (OA) is still controversial. We investigated the effect of PRP injections in patients with knee OA based on decreasing pain, improving function, global assessment and changes regarding joint imaging.
  
  
  METHODS
  We performed a comprehensive, systematic literature search in computerised databases (MEDLINE, EMBASE, CINAHL, CENTRAL, Web of Science and PEDro) until June 2014 for randomised or non-randomised controlled trials. These were graded for risk of bias and a level of evidence was provided. If possible, meta-analysis was performed.
  
  
  RESULTS
  Ten trials were included. In these, intra-articular PRP injections were more effective for pain reduction (mean difference (MD) -2.45; 95% CI -2.92 to -1.98; p value <0.00001 and MD -2.07; 95% CI -2.59 to -1.55; p value <0.00001, single and double PRP injections, respectively) compared with placebo at 6 months postinjection. Intra-articular PRP injections were compared with hyaluronic acid and showed a statistically significant difference in favour of PRP on pain reduction based on the visual analogue scale and numeric rating scale (standardised mean difference -0.92; 95% CI -1.20 to -0.63; p value <0.00001) at 6 months postinjection. Almost all trials revealed a high risk of bias.
  
  
  CONCLUSIONS
  On the basis of the current evidence, PRP injections reduced pain more effectively than did placebo injections in OA of the knee (level of evidence: limited due to a high risk of bias). This significant effect on pain was also seen when PRP injections were compared with hyaluronic acid injections (level of evidence: moderate due to a generally high risk of bias). Additionally, function improved significantly more when PRP injections were compared with controls (limited to moderate evidence). More large randomised studies of good quality and low risk of bias are needed to test whether PRP injections should be a routine part of management of patients with OA of the knee.
authors.affiliation: Department of Physiotherapy, Meander Medical Centre, Amersfoort, The Netherlands Department of Clinical Epidemiology and Biostatistics, Academic Medical Center, University of Amsterdam, Amersfoort, The Netherlands.
authors.forename: Augustinus B M
authors.initials: AB
authors.lastname: Laudy
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, Academic Medical Center, University of Amsterdam, Amersfoort, The Netherlands.
authors.forename: Eric W P
authors.initials: EW
authors.lastname: Bakker
authors.affiliation: Department of Sport Medical Care, FC Utrecht, Utrecht, The Netherlands.
authors.forename: Mark
authors.initials: M
authors.lastname: Rekers
authors.affiliation: Department of Sports Medicine, Bergman Clinics, Naarden, The Netherlands The Sportsphysician Group, Saint Lucas Hospital, Amsterdam, The Netherlands.
authors.forename: Maarten H
authors.initials: MH
authors.lastname: Moen
mesh_terms: D002986:Clinical Trials as Topic; D006801:Humans; D007270:Injections, Intra-Articular; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000628:therapy*; D010146:Pain / Q000209:etiology; D017060:Patient Satisfaction; D053657:Platelet-Rich Plasma; D011785:Quality Assurance, Health Care; D016896:Treatment Outcome
keywords: Cartilage; Muscle; Sports medicine; Tendon