Does PRP work? Why study answers differ

What to look for in a study result

First, check which joint the study examined. A knee result doesn't settle care for a hip. Then see when the people reported any relief. Early and later relief answer different needs.

Next, ask what the study compared with PRP. Some studies use cortisone, while others use a salt-water shot. People may also improve with time and basic care. Knowing the comparison tells you what the result means.

What the mixed results mean

Some knee studies find more relief with PRP later on. Other studies find about the same relief as salt water. That doesn't mean nobody feels better after PRP. It means a study can't promise what you'll feel.

An average study result combines pain reports from many people. Your own change could be larger, smaller, or absent. Research also hasn't shown that PRP rebuilds a worn joint. Relief from soreness isn't proof that the joint was repaired.

What to ask at your visit

Ask whether the study involved your kind of joint soreness. Find out exactly how the clinic will spin your blood. You'll also want a date for checking any relief. Don't leave cost and recovery questions until the end.

After your exam, QC Kinetix medical providers may discuss natural pain treatments, including regenerative care using blood drawn from you. Ask which daily task might become easier if it works. If you don't improve, ask what care would come next. The answer should name the treatment, not another broad term.

Sources

1. A Bayesian network meta-analysis of 48 Level I-II randomized trials (9,338 knees) with a minimum 6-month follow-up ranked the four commonest intra-articular injections. HA and PRP both significantly improved pain versus placebo; HA, PRP and BMAC all significantly improved function versus placebo. SUCRA rankings were PRP 91.54, BMAC 76.46, HA 53.12, corticosteroid 15.18 and placebo 13.70 - corticosteroid ranked barely above placebo at six months and beyond.

   Jawanda H, et al. — Platelet-Rich Plasma, Bone Marrow Aspirate Concentrate, and Hyaluronic Acid Injections Outperform Corticosteroids in Pain and Function Scores at a Minimum of 6 Months as Intra-Articular Injections for Knee Osteoarthritis: A Systematic Review and Network Meta-analysis.. Arthroscopy, 2024. DOI: 10.1016/j.arthro.2024.01.037.

2. A network meta-analysis restricted to LARGE randomized trials (at least 100 patients per group; 57 RCTs, 22,795 participants, 18 intra-articular interventions) found treatment effects were consistently larger in the 35 high-risk-of-bias trials than in the 22 low/unclear-risk trials. In the main analysis excluding high-risk trials, triamcinolone had the highest probability of exceeding the minimal important difference at weeks 2 and 6; hyaluronic acid had no effect on pain (SMD -0.04, 95% CrI -0.19 to 0.11, 11 trials) but higher odds of dropouts due to adverse events (OR 2.01) and of serious adverse events (OR 1.86). The effects of 16 of the 18 interventions were smaller than the MID and most were consistent with placebo effects.

   Pereira TV, et al. — Effectiveness and safety of intra-articular interventions for knee and hip osteoarthritis based on large randomized trials: A systematic review and network meta-analysis.. Osteoarthritis and Cartilage, 2025. DOI: 10.1016/j.joca.2024.08.014.

3. RESTORE, the largest and most rigorously blinded placebo-controlled PRP trial in knee OA (n=288, participant-, injector- and assessor-blinded), gave three weekly injections of a commercial leukocyte-poor PRP or saline. At 12 months the change in knee pain was -2.1 vs -1.8 points (difference -0.4; 95% CI -0.9 to 0.2; P=.17) and the change in medial tibial cartilage volume was -1.4% vs -1.2% (difference -0.2%; P=.81). Twenty-nine of 31 prespecified secondary outcomes showed no between-group difference. The authors concluded the findings do not support the use of PRP for knee OA.

   Bennell KL, 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.

4. A meta-analysis of 34 RCTs (1,403 PRP knees vs 1,426 controls) found WOMAC favoured PRP over placebo at 12 months and over hyaluronic acid at 6 and 12 months, and favoured PRP over steroids on VAS pain, KOOS pain, daily function and quality of life at 6 months. Crucially, the authors state that the superiority of PRP DID NOT REACH the minimal clinically important difference for any outcome and the quality of evidence was low.

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

5. The 2025 Cochrane review of stem cell injections for knee osteoarthritis pooled 25 randomised trials (1,341 participants) and found that, compared with placebo injection, stem cell injection MAY slightly improve pain (1.2 points better on a 0-10 scale, 7 studies, 445 participants) and function (14.2 points better on a 0-100 scale, 7 studies, 432 participants) up to six months - both rated LOW-certainty evidence, downgraded for indirectness (cell source, preparation and dose varied across studies) and suspected publication bias, since up to three larger RCTs were conducted and withdrawn before reporting results. Radiographic progression was not assessed in any included study.

   Whittle SL, et al. — Stem cell injections for osteoarthritis of the knee.. Cochrane Database of Systematic Reviews, 2025. DOI: 10.1002/14651858.CD013342.pub2.

6. FDA states verbatim of stem cell products, stromal vascular fraction (adipose-derived cells), umbilical cord blood, Wharton's jelly, amniotic fluid and exosome products: 'None of these products have been approved for the treatment of any orthopedic condition, such as osteoarthritis, tendonitis, disc disease, tennis elbow, back pain, hip pain, knee pain, neck pain, or shoulder pain.' The only FDA-approved stem cell products in the United States are blood-forming (hematopoietic progenitor) cells derived from umbilical cord blood, approved only for disorders of blood production, and there are currently NO FDA-approved exosome products.

   U.S. Food and Drug Administration — Consumer Alert on Regenerative Medicine Products Including Stem Cells and Exosomes. FDA (Center for Biologics Evaluation and Research), 2020.

7. A frequentist network meta-analysis with a minimum 6-month follow-up found all intra-articular treatments EXCEPT corticosteroid significantly better than placebo. PRP had the highest probability of efficacy for pain, function and both combined, followed by plasma rich in growth factors (PRGF), then HA, then corticosteroid, then placebo.

   Singh H, et al. — Relative Efficacy of Intra-articular Injections in the Treatment of Knee Osteoarthritis: A Systematic Review and Network Meta-analysis.. American Journal of Sports Medicine, 2022. DOI: 10.1177/03635465211029659.

8. A meta-analysis of the PLACEBO arms of 73 double-blind trials (5,895 patients) quantified what a saline knee injection alone achieves: statistically and clinically significant improvement in pain, function and quality of life at 1, 3 and 6 months, with responder rates exceeding 50% at all three time points, peaking around 4-8 months and declining by 12 months. Placebo response was stronger in trials with more female participants and in more recently published trials.

   Previtali D, 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.