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The published research

Platelet-rich plasma

A summary of the peer-reviewed research on PRP — which uses are well supported, which are not, and what the trials actually measured. Every statement below is linked to its source study.

  • 12 peer-reviewed sources
  • Every citation verified
  • Reviewed by a licensed ND
Medically reviewed by Nikodemas McNulty, ND Licensed naturopathic doctor and founder of Nature & Science Medicine. Reviewed September 2026. See our doctors

What the research shows

The rationale for PRP is that platelets carry the signalling proteins tissue repair runs on. Experimental work confirms the payload is real and that it is released over time: in a controlled animal study, injectable platelet-rich fibrin produced higher levels of VEGF, EGF, TGF-β, PDGF and FGF than saline over fourteen days, with epithelialisation beginning by day three and more prominent connective-tissue maturation 1. That study was conducted in rats, and is included here as mechanism rather than as evidence of a clinical result.

The knee is where PRP has been tested most, and where the evidence is strongest — with one qualification that turns out to matter enormously. A 2025 meta-analysis in the American Journal of Sports Medicine pooled 18 randomised controlled trials covering 1,995 patients. PRP was statistically superior to placebo at every follow-up point, and crossed the threshold for a clinically meaningful difference at three and six months for pain and at every point for function. The subanalysis is the part worth reading twice: high-platelet PRP delivered clinically significant pain relief at three, six and twelve months, while low-platelet PRP failed to offer a perceivable benefit on the pain scale at all 2. The same preparation, at a different concentration, is a different treatment.

That result sits on top of a consistent comparative literature. A 2021 systematic review and meta-analysis of 18 level 1 studies found PRP outperformed hyaluronic acid in knee osteoarthritis 3; a 2020 meta-analysis of 20 randomised trials reached the same conclusion 4; and an earlier meta-analysis of 14 randomised trials in 1,423 participants found the benefit over control emerged and held over time rather than fading 5.

Tendon problems are the second well-supported area. A 2025 systematic review and meta-analysis of 27 randomised controlled trials in 1,779 patients compared PRP against corticosteroid injection across rotator cuff injury, tennis elbow, plantar fasciitis and tenosynovitis. The pattern was consistent and clinically interesting: corticosteroid tended to win early, PRP tended to win later. In plantar fasciitis there was no difference at one and three months, but by six months the PRP group had significantly better pain and function scores 6. A separate randomised controlled trial found two ultrasound-guided PRP injections more beneficial than dry needling in tennis elbow 7.

For hair, the picture is positive but the reviewers were cautious about it. A systematic review and meta-analysis in Blood Transfusion covering 27 controlled trials and 1,117 subjects found PRP increased hair density against saline injection over medium-term follow-up by a mean of 25.6 hairs per cm² — and graded that evidence as low certainty, because preparations, activation methods and injection schedules varied so much between studies that the results could not all be pooled 8. A 2024 meta-analysis of six studies in 343 participants found PRP combined with minoxidil outperformed either alone on hair density and hair diameter 9.

In facial work, the strongest evidence is for acne scarring rather than for ageing skin. A meta-analysis of fourteen controlled studies in 472 patients found microneedling with PRP produced better scar-scale outcomes and markedly higher patient satisfaction than microneedling alone, with no significant difference in severe adverse events 10.

Running underneath all of this is a problem the field acknowledges openly: PRP is not one product. Preparation protocols, platelet concentration, leucocyte content and activation all vary between clinics and between studies, and the classification systems introduced to make trials comparable are still inconsistently applied 12. That is the honest reason two studies of "PRP" can disagree, and the reason the platelet-concentration finding above is the single most useful thing on this page.

Where the evidence is thin

We would rather tell you this ourselves than have you find it somewhere else. These are the parts of the picture that do not favour the treatment, or where the research simply has not been done.

For facial skin ageing, a well-run trial found no benefit

In a randomised split-face trial at Mayo Clinic, 18 women received PRP injections to one side of the face and saline to the other, with microneedling performed across the whole face. There was no evidence of improvement in skin laxity, wrinkles or roughness for PRP over saline at any follow-up point out to 24 weeks 11.

It is a small study and its authors noted that participant age and the sensitivity of the assessment methods may have contributed. But it is a randomised, controlled, split-face design — one of the more rigorous ways to test this — and it did not find what it was looking for. We offer PRP facial treatments and we are not going to claim a result the best-designed trial did not produce.

Nebulized PRP has no clinical evidence base we could find

We searched for clinical trials of nebulized platelet-rich plasma and found none to summarise. It is on our menu and it is priced openly on the PRP page. It does not get an evidence section here, because there is nothing to put in one.

The hair-loss evidence was graded low-certainty by its own reviewers

The direction of effect is consistent and positive. The confidence in it is not high, and that is the reviewers' assessment rather than ours — driven by the wide variation in how PRP was prepared and administered across the trials.

"PRP" means different things in different clinics

Because preparation methods vary so widely, results from one clinic's protocol do not automatically transfer to another's. This is a real limitation of the whole literature, and it is why the platelet-concentration finding matters more than any single headline result. Ask any provider — including us — what is actually in the syringe.

Supporting studies

  • 1

    Platelet concentrates release a measurable payload of repair signalling proteins — VEGF, EGF, TGF-β, PDGF and FGF — over about two weeks.

    In this controlled split-mouth animal study, 40 rats received injectable platelet-rich fibrin in the right buccal area and saline in the left. Cytokeratin, FGF, PDGF, TGF and VEGF expression were assessed by immunohistochemistry, with gene expression analysis for EGF, TGF-β and VEGF. Epithelialisation began on the third day and connective-tissue maturation was more prominent in the treated group. Release of VEGF, EGF, TGF-β, PDGF and FGF was higher in the treated group across 14 days, and changes in TGF-β at 14 days and VEGF at 21 days reached statistical significance. ⚠️ This is an animal study and establishes mechanism only. It is not evidence of a clinical outcome in people, and is labelled as such deliberately.

    Preclinical (animal study) Lektemur Alpan A, et al. Evaluation of the effect of injectable platelet-rich fibrin (i-PRF) in wound healing and growth factor release in rats: a split-mouth study. Growth Factors. 2024. PMID 38058166 ↗

  • 2

    Across 18 randomised trials in 1,995 patients, high-platelet PRP produced clinically meaningful pain relief at 3, 6 and 12 months — while low-platelet PRP produced no perceivable benefit on the pain scale.

    From 5,499 articles retrieved, 18 randomised controlled trials covering 1,995 patients were included. PRP was statistically superior to placebo in both VAS and WOMAC scores at all follow-up points, exceeding the minimal clinically important difference at 3 and 6 months for VAS and at all points for WOMAC. In the subanalysis by platelet concentration, high-platelet PRP exceeded the MCID for pain relief against placebo at 3, 6 and 12 months, whereas low-platelet PRP failed to offer a clinically perceivable benefit on VAS. On WOMAC, both provided clinically significant improvement at 3 and 6 months, but only the high-platelet group maintained a statistically significant benefit at 12 months. This is the clearest published demonstration that concentration, not simply the label 'PRP', determines the result.

    Meta-analysis of randomised controlled trials Bensa A, et al. PRP Injections for the Treatment of Knee Osteoarthritis: The Improvement Is Clinically Significant and Influenced by Platelet Concentration: A Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2025. PMID 39751394 ↗

  • 3

    Pooling 18 level 1 randomised trials, patients treated with PRP for knee osteoarthritis could be expected to do better than those treated with hyaluronic acid.

    Eighteen studies, all level 1 evidence, met the inclusion criteria in this systematic review and meta-analysis comparing intra-articular platelet-rich plasma against hyaluronic acid in knee osteoarthritis. The authors concluded that patients undergoing treatment for knee osteoarthritis with PRP can be expected to experience improved clinical outcomes compared with hyaluronic acid. Hyaluronic acid is a mainstream comparator rather than a placebo, which makes this a meaningful benchmark.

    Systematic review and meta-analysis of level 1 randomised controlled trials Belk JW, et al. Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2021. PMID 32302218 ↗

  • 4

    An independent meta-analysis of 20 randomised trials reached the same conclusion — PRP outperformed hyaluronic acid in knee osteoarthritis.

    Twenty randomised controlled trials were enrolled in this meta-analysis comparing intra-articular platelet-rich plasma injection against hyaluronic acid for knee osteoarthritis. The authors concluded that intra-articular PRP injection appeared to be more efficacious than hyaluronic acid. Included alongside the American Journal of Sports Medicine review above because independent replication by a separate team, on a partly different trial set, is more informative than any single review.

    Meta-analysis of randomised controlled trials Tang JZ, et al. Platelet-rich plasma versus hyaluronic acid in the treatment of knee osteoarthritis: a meta-analysis. Journal of Orthopaedic Surgery and Research. 2020. PMID 32912243 ↗

  • 5

    Across 14 randomised trials in 1,423 participants, the benefit of PRP over control emerged and was sustained over time rather than fading.

    Fourteen randomised controlled trials comprising 1,423 participants were included. Intra-articular PRP injections showed significantly better outcomes than the control interventions on pain and on total WOMAC scores, with the analysis structured specifically to examine how the effect behaved over follow-up time. The authors concluded that intra-articular PRP injections are probably more efficacious than the comparators studied. Earlier and smaller than the 2025 analysis, and consistent with it.

    Systematic review and meta-analysis of randomised controlled trials Shen L, et al. The temporal effect of platelet-rich plasma on pain and physical function in the treatment of knee osteoarthritis: systematic review and meta-analysis of randomized controlled trials. Journal of Orthopaedic Surgery and Research. 2017. PMID 28115016 ↗

  • 6

    Across 27 randomised trials in 1,779 patients with tendon problems, corticosteroid tended to win early and PRP tended to win later.

    Twenty-seven randomised controlled trials enrolling 1,779 patients were pooled, covering 8 rotator cuff injuries, 7 cases of humeral external epicondylitis, 10 of plantar fasciitis and 2 of tenosynovitis. In rotator cuff injury there was no significant group difference at one month, but at three months VAS scores favoured PRP (OR -1.64, 95% CI -2.97 to -0.31, P = 0.02). In plantar fasciitis there was no significant difference at one and three months, but at six months the PRP group showed significantly better VAS and AOFAS scores (OR -1.41, 95% CI -1.88 to -0.44, P < 0.00001; OR 7.19, 95% CI 2.41 to 11.91, P = 0.003). The authors concluded PRP improves pain and function in tendinopathy with mid-term efficacy superior to corticosteroids, while noting long-term efficacy remains to be verified.

    Systematic review and meta-analysis of randomised controlled trials Ye Z, et al. Platelet-rich plasma and corticosteroid injection for tendinopathy: a systematic review and meta-analysis. BMC Musculoskeletal Disorders. 2025. PMID 40200209 ↗

  • 7

    In tennis elbow, two ultrasound-guided PRP injections outperformed dry needling on pain scores.

    This randomised controlled trial compared ultrasound-guided platelet-rich plasma injection against dry needling in patients with lateral epicondylitis, with significant improvement in visual analogue scale pain scores reported. The authors concluded that two ultrasound-guided PRP injections are the more beneficial non-surgical option of the two compared. Note the ultrasound guidance: as with the ozone back-pain literature, how accurately an injection is placed is part of whether it works.

    Randomised controlled trial Sharma GK, et al. Comparison of efficacy of ultrasound-guided platelet rich plasma injection versus dry needling in lateral epicondylitis - a randomised controlled trial. Journal of Ultrasound. 2024. PMID 38393452 ↗

  • 8

    Pooling 27 controlled trials in 1,117 subjects, PRP increased hair density against saline by about 25.6 hairs per cm² — evidence the reviewers graded as low certainty.

    Twenty-seven controlled trials with 1,117 subjects met the inclusion criteria: 18 trials (713 subjects) in androgenetic alopecia and 9 (404 subjects) in alopecia areata. Eleven used a split-head design. PRP was compared against saline injection in 18 studies, local steroid injection in 4, and other comparators in 5. Compared with saline, PRP increased hair density over medium-term follow-up by a mean difference of 25.6 hairs/cm² (95% CI 2.62 to 48.57). The reviewers rated this evidence as low certainty, and noted that heterogeneity in PRP types (activated versus non-activated) and in administration schedules meant not all outcome data could be pooled. The low-certainty grade is the reviewers' own and is reported here rather than omitted.

    Systematic review and meta-analysis of controlled trials Cruciani M, et al. Platelet-rich plasma for the treatment of alopecia: a systematic review and meta-analysis. Blood Transfusion. 2023. PMID 34967722 ↗

  • 9

    PRP combined with minoxidil outperformed either treatment alone on both hair density and hair diameter.

    Six studies involving 343 participants were pooled. PRP combined with minoxidil significantly improved hair growth compared with minoxidil alone or PRP alone, with a weighted mean difference of 9.14 (95% CI 6.57 to 11.70) for hair density and 4.72 (95% CI 3.21 to 6.23) for hair diameter. Patients receiving the combination also reported higher satisfaction rates than those on either single treatment. Relevant because it suggests PRP is best considered as part of a plan rather than as a standalone substitute for established therapy.

    Meta-analysis of controlled studies Xiao C, et al. Meta-Analysis of Efficacy of Platelet-Rich Plasma Combined with Minoxidil for Androgenetic Alopecia. Aesthetic Plastic Surgery. 2024. PMID 38789807 ↗

  • 10

    For acne scarring, adding PRP to microneedling produced better scar-scale outcomes and markedly higher patient satisfaction than microneedling alone.

    Four randomised and ten split-face non-randomised controlled studies with 472 patients were pooled. Compared with microneedling alone, microneedling combined with PRP was associated with increased odds of greater than 50% clinical improvement on Goodman's qualitative scale and a significantly improved mean GQS score (mean difference -0.32, 95% CI -0.44 to -0.20, p < 0.001, I² = 0%). Patient satisfaction was substantially higher with the combination (OR 4.15, 95% CI 2.13 to 8.09, p < 0.001). Rates of severe erythema and severe oedema did not differ significantly between groups. Note that ten of the fourteen studies were non-randomised, which tempers the strength of the conclusion.

    Meta-analysis of randomised and non-randomised controlled studies Kang C, et al. Combined Effect of Microneedling and Platelet-Rich Plasma for the Treatment of Acne Scars: A Meta-Analysis. Frontiers in Medicine. 2021. PMID 35237616 ↗

  • 11

    A randomised split-face trial found no benefit of PRP over saline for facial skin ageing.

    In this prospective randomised clinical trial at Mayo Clinic Florida, 18 women with facial ageing were randomised to receive PRP injections to one side of the face and saline injections to the other, with microneedling performed across the entire face after injection. Outcomes were assessed by physician assessment, photographs and satisfaction questionnaires at baseline, 16 and 24 weeks. There was no evidence of improvement — and a suggestion of worsening — in skin laxity and rhytides from baseline for both PRP and saline (all P ≤ 0.004), and no notable difference in skin roughness (all P ≥ 0.19). The degree of change was similar for PRP and saline. The authors concluded PRP did not appear effective for facial skin ageing in this population, noting that participant age (over 45) and less-sensitive evaluation methods may have contributed. ⚠️ This study does not support the use of PRP for facial skin ageing. It is on this page because leaving it off would misrepresent the literature.

    Randomised controlled trial (split-face) Pincelli TP, et al. Evaluation of Platelet-rich Plasma and Microneedling for Facial Skin Rejuvenation. Plastic and Reconstructive Surgery — Global Open. 2024. PMID 38798929 ↗

  • 12

    "PRP" is not one standardised product, and the classification systems built to make studies comparable are still applied inconsistently.

    This review revisits the foundational classification of platelet concentrates, which separates them by leucocyte content and fibrin architecture — pure platelet-rich plasma, leucocyte- and platelet-rich plasma, pure platelet-rich fibrin, and leucocyte- and platelet-rich fibrin. The framework exists because preparation protocol, platelet concentration, leucocyte content and activation method all materially change what is being injected, and without a shared vocabulary trials cannot be meaningfully compared. Included here because it is the honest explanation for why two studies of 'PRP' can disagree, and why asking what is actually in the syringe is a reasonable question to put to any provider.

    Review of a classification framework Marín Fermín T, et al. Review of Dohan Eherenfest et al. (2009) on "Classification of platelet concentrates: From pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)". Journal of ISAKOS. 2024. PMID 37562572 ↗

References

  • 1Lektemur Alpan A, et al. Evaluation of the effect of injectable platelet-rich fibrin (i-PRF) in wound healing and growth factor release in rats: a split-mouth study. Growth Factors. 2024. PMID 38058166 ↗
  • 2Bensa A, et al. PRP Injections for the Treatment of Knee Osteoarthritis: The Improvement Is Clinically Significant and Influenced by Platelet Concentration: A Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2025. PMID 39751394 ↗
  • 3Belk JW, et al. Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2021. PMID 32302218 ↗
  • 4Tang JZ, et al. Platelet-rich plasma versus hyaluronic acid in the treatment of knee osteoarthritis: a meta-analysis. Journal of Orthopaedic Surgery and Research. 2020. PMID 32912243 ↗
  • 5Shen L, et al. The temporal effect of platelet-rich plasma on pain and physical function in the treatment of knee osteoarthritis: systematic review and meta-analysis of randomized controlled trials. Journal of Orthopaedic Surgery and Research. 2017. PMID 28115016 ↗
  • 6Ye Z, et al. Platelet-rich plasma and corticosteroid injection for tendinopathy: a systematic review and meta-analysis. BMC Musculoskeletal Disorders. 2025. PMID 40200209 ↗
  • 7Sharma GK, et al. Comparison of efficacy of ultrasound-guided platelet rich plasma injection versus dry needling in lateral epicondylitis - a randomised controlled trial. Journal of Ultrasound. 2024. PMID 38393452 ↗
  • 8Cruciani M, et al. Platelet-rich plasma for the treatment of alopecia: a systematic review and meta-analysis. Blood Transfusion. 2023. PMID 34967722 ↗
  • 9Xiao C, et al. Meta-Analysis of Efficacy of Platelet-Rich Plasma Combined with Minoxidil for Androgenetic Alopecia. Aesthetic Plastic Surgery. 2024. PMID 38789807 ↗
  • 10Kang C, et al. Combined Effect of Microneedling and Platelet-Rich Plasma for the Treatment of Acne Scars: A Meta-Analysis. Frontiers in Medicine. 2021. PMID 35237616 ↗
  • 11Pincelli TP, et al. Evaluation of Platelet-rich Plasma and Microneedling for Facial Skin Rejuvenation. Plastic and Reconstructive Surgery — Global Open. 2024. PMID 38798929 ↗
  • 12Marín Fermín T, et al. Review of Dohan Eherenfest et al. (2009) on "Classification of platelet concentrates: From pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)". Journal of ISAKOS. 2024. PMID 37562572 ↗

On our sourcing. Every one of the 12 sources on this page was pulled directly from the live PubMed database — the US National Library of Medicine's index of biomedical literature — confirming that each PubMed ID points to the exact paper cited, with a matching author, title, journal and year. Click any reference to read the original. Where a study is preclinical, or was conducted in animals rather than people, this page says so on that study.

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This page summarises published research about platelet-rich plasma. It is educational information about that research. It is not a claim that this or any Nature & Science Medicine service diagnoses, treats, cures or prevents any disease, and it is not a substitute for a consultation with a licensed provider. Individual results vary.