What the research says about PRP

Read knee results with care

PRP uses a machine to separate your blood and keep extra platelets. These tiny blood cells help begin healing after a cut, but knee results are mixed.

Some studies found more relief than other common procedures at checks months later. A large knee trial found no clear difference from saline, a saltwater shot used for comparison.

That trial also found no clear cartilage change, so PRP can’t promise joint repair. Different blood preparations and visit schedules make broad claims hard to trust. Ask the clinician which of these studies looked at a joint like yours.

Match the research to your sore area

A knee study can’t answer every question about a shoulder, hip, or tendon. One study may compare PRP with saltwater for months, while another compares a common procedure for a different length of time.

QC Kinetix discusses natural pain treatments in Chandler; here, that means PRP prepared there from the patient’s blood. The clinician still needs to link the research to why you’re sore.

Ask which study fits your body part and how relief would be checked. Also ask when the clinician would decide the treatment hasn’t helped.

Answer does prp work without promises

So, does prp work? It may help some people, but good research doesn’t support a promise.

Relief after a procedure can also come from rest, exercise, time, or other care. One person’s result can’t prove which part helped.

The useful answer concerns your sore area and its known cause. Cost, health, daily tasks, and other choices belong in that talk before care begins.

Sources

1. In the RESTORE trial - the largest placebo-controlled PRP trial in knee osteoarthritis - 288 adults aged 50+ with symptomatic Kellgren-Lawrence grade 2-3 medial knee OA received three weekly intra-articular injections of leukocyte-poor PRP from a commercial system or saline placebo. At 12 months the mean change in knee pain was -2.1 points with PRP versus -1.8 with saline (difference -0.4; 95% CI -0.9 to 0.2; P=.17) against a minimum clinically important difference of 1.8, and the change in medial tibial cartilage volume was -1.4% versus -1.2% (difference -0.2%; 95% CI -1.9% to 1.5%; P=.81). Twenty-nine of 31 prespecified secondary outcomes showed no significant between-group difference. The authors concluded the findings do not support use of PRP for knee OA.

   Bennell KL, Paterson KL, Metcalf BR, et al. — Effect of Intra-articular Platelet-Rich Plasma vs Placebo Injection on Pain and Medial Tibial Cartilage Volume in Patients With Knee Osteoarthritis: The RESTORE Randomized Clinical Trial. JAMA, 2021. DOI: 10.1001/jama.2021.19415.

2. A meta-analysis of 34 randomized trials (1403 PRP knees, 1426 control knees) found WOMAC favoured PRP over placebo at 12 months (P=.02) and over hyaluronic acid at 6 and 12 months (P<.001), and favoured PRP over steroids on VAS pain and KOOS at 6 months. Critically, the authors reported that the superiority of PRP did NOT reach the minimal clinically important difference for any outcome, and graded the quality of evidence as low.

   Filardo G, Previtali D, Napoli F, et al. — PRP Injections for the Treatment of Knee Osteoarthritis: A Meta-Analysis of Randomized Controlled Trials. Cartilage, 2021. DOI: 10.1177/1947603520931170.

3. A meta-analysis of eight studies (648 patients, mean age 59) judged at low risk of bias found PRP significantly better than intra-articular corticosteroid for knee OA symptoms at 3, 6 and 9 months (P<0.01), with the largest effects at 6 months (SMD -0.78; 95% CI -1.34 to -0.23) and 9 months (SMD -1.63; 95% CI -2.14 to -1.12). This is the strongest available case for PRP as a longer-acting alternative to a steroid shot.

   McLarnon M, Heron N — Intra-articular platelet-rich plasma injections versus intra-articular corticosteroid injections for symptomatic management of knee osteoarthritis: systematic review and meta-analysis. BMC Musculoskeletal Disorders, 2021. DOI: 10.1186/s12891-021-04308-3.

4. PATH-2 randomised 230 adults with acute Achilles tendon rupture managed non-surgically to PRP or a placebo dry-needle injection across 19 UK hospitals, with a central laboratory confirming the PRP was of good quality with the expected growth-factor content. At 24 weeks there was no detectable difference in muscle-tendon function (limb symmetry index 34.7% versus 38.5%; adjusted mean difference -3.9%; 95% CI -10.5% to 2.7%) or in any secondary outcome or adverse-event rate.

   Keene DJ, Alsousou J, Harrison P, et al. — Platelet rich plasma injection for acute Achilles tendon rupture: PATH-2 randomised, placebo controlled, superiority trial. BMJ, 2019. DOI: 10.1136/bmj.l6132.

5. A meta-analysis of 73 articles covering 5,895 patients quantified the PLACEBO response to intra-articular injection in knee osteoarthritis: statistically and clinically significant improvements in pain, function and quality of life at 1, 3 and 6 months, with responder rates above 50% at each of those points, declining by 12 months. The placebo response was stronger in trials with more female participants and in more recently published trials. This is why an uncontrolled 'our patients improved' figure carries almost no information.

   Previtali D, Boffa A, Di Laura Frattura G, et al. — Placebo response to intra-articular injections in knee osteoarthritis: magnitude, evolution over time, and influencing factors. A systematic review and meta-analysis with meta-regression. EFORT Open Reviews, 2025. DOI: 10.1530/EOR-2025-0022.

6. A systematic review of 105 clinical PRP studies in orthopaedics published 2006-2016 found that only 11 (10%) described the preparation protocol clearly enough for another investigator to repeat it, and only 17 (16%) reported any quantitative metric of the final PRP composition. The authors concluded that the current reporting of PRP preparation and composition does not allow the PRP products actually delivered to patients to be compared between studies.

   Chahla J, Cinque ME, Piuzzi NS, et al. — A Call for Standardization in Platelet-Rich Plasma Preparation Protocols and Composition Reporting: A Systematic Review of the Clinical Orthopaedic Literature. Journal of Bone and Joint Surgery (American), 2017. DOI: 10.2106/JBJS.16.01374.

7. The devices used to spin PRP at the point of care are cleared by FDA as clinical centrifuges, product code JQC, a Class I device under 21 CFR 862.2050 - for example the Biomet GPS Platelet Separation Kit (K030555, cleared 2003) and the Harvest SmartPrep2 / SmartPrep Platelet Concentration System (K103340, cleared 2010). That clearance covers the equipment that separates blood. It is not an FDA approval of platelet-rich plasma as a treatment for osteoarthritis, tendinopathy or any other orthopedic condition, and copy must never blur the two.

   U.S. Food and Drug Administration (Center for Devices and Radiological Health) — 510(k) Premarket Notification database and Product Classification: JQC, Centrifuges (Micro, Ultra, Refrigerated) For Clinical Use, 21 CFR 862.2050. FDA accessdata (CDRH device databases), 2003.

8. A systematic review of 29 randomized trials of PRP for knee OA that reported a platelet count, concentration or dose found that the 28 treatment arms with statistically significant positive outcomes at 6 months had a mean platelet dose of 5,500 (+/-474) x 10^6, while the three arms without a positive difference averaged 2,302 (+/-437) x 10^6 (P<.01). The same separation held at 12 months: 5,464 versus 2,253 x 10^6 (P<.05).

   Berrigan WA, Bailowitz Z, Park A, et al. — A Greater Platelet Dose May Yield Better Clinical Outcomes for Platelet-Rich Plasma in the Treatment of Knee Osteoarthritis: A Systematic Review. Arthroscopy, 2025. DOI: 10.1016/j.arthro.2024.03.018.