What do medical studies say about PRP?

Does PRP help a sore knee?

Some studies found less soreness and easier knee use after PRP. A large, careful study found no clear benefit over salt water. The research is mixed, so neither result settles the question.

Both groups in the large study reported less soreness. That doesn't mean salt water repaired their knees. Time and receiving care can change how people feel. The study couldn't credit the extra relief to PRP.

Other reviews brought many smaller studies together and favored PRP. Their authors said the change might be too slight for patients to feel. That could mean no clear difference in walking, sleep or daily tasks. Preparation methods vary among clinics, which can also change the findings.

How might prp vs cortisone feel over time?

Studies comparing PRP with cortisone found that timing can matter. Cortisone may help sooner, while PRP may last longer when it helps. The clearer differences appeared after several months, not the next day. Still, PRP won't work for every sore knee.

QC Kinetix can discuss regenerative treatment options after checking the joint. Regenerative means the care is intended to support the body's repair work. Staff prepare PRP on site from blood drawn from the patient. The visit can cover earlier care, painful tasks and an available X-ray.

Cost and recovery time also belong in that conversation. Some research compared one PRP treatment with three given a week apart. Ask how many visits are proposed and when results would be judged. The clinician can also explain the soreness expected after each choice.

What do the studies leave unanswered?

Studies can't show whether PRP will keep one person from surgery. They also haven't shown that worn cartilage grows back. Most favorable knee studies involved mild or moderate wear. A very worn joint may call for a different discussion.

The exam matters more than a broad success rate. Ask what the clinician found and why PRP may or may not fit. Ask when you could fairly judge whether PRP reduced your soreness. A clear answer includes the chance that it won't help.

Sources

1. 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.

2. The ESSKA-ORBIT European consensus on blood-derived orthobiologics graded 28 question-statement sets; only 9 of 28 had high-level scientific support. Three statements reached grade A: that there is enough preclinical and clinical evidence to support PRP use in knee OA; that clinical evidence shows effectiveness in MILD TO MODERATE knee OA (KL grade 3 or lower); and that PRP provides a longer effect than the short-term effect of corticosteroid with a safer profile. The panel regarded PRP as a valid and possible first-line injectable option for KL grades 1-3.

   Laver L, et al. — The use of injectable orthobiologics for knee osteoarthritis: A European ESSKA-ORBIT consensus. Part 1-Blood-derived products (platelet-rich plasma).. Knee Surgery, Sports Traumatology, Arthroscopy, 2024. DOI: 10.1002/ksa.12077.

3. 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.

4. A meta-analysis of 18 Level I trials (811 PRP vs 797 HA patients, mean follow-up 11.1 months) found mean WOMAC total improvement of 44.7% with PRP versus 12.6% with HA (P<.01). Six of 11 VAS-based studies and 3 of 6 IKDC-based studies favoured PRP significantly. In the subanalysis, leukocyte-POOR PRP was associated with significantly better subjective IKDC scores than leukocyte-rich PRP.

   Belk JW, et al. — Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials.. American Journal of Sports Medicine, 2021. DOI: 10.1177/0363546520909397.

5. A meta-analysis of 8 trials (648 patients, judged at low risk of bias overall) comparing intra-articular PRP with intra-articular corticosteroid found PRP significantly better for pain, stiffness and function at 3, 6 and 9 months (P<0.01), with the largest effects at 6 months (SMD -0.78) and 9 months (SMD -1.63). Three PRP injections a week apart outperformed a single injection over 12 months.

   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.

6. A randomized controlled trial compared a SINGLE ultrasound-guided injection of leukocyte-rich PRP (n=30) with micro-fragmented adipose tissue (n=28) in KL 1-4 knee OA. Both groups improved clinically meaningfully from baseline, and there was no significant difference in the primary outcome (KOOS-Pain at 6 months: 80.38 vs 81.61; P=.67) or in any other score - despite MFAT requiring a lipoaspiration procedure and PRP requiring only a blood draw.

   Baria M, et al. — Platelet-Rich Plasma Versus Microfragmented Adipose Tissue for Knee Osteoarthritis: A Randomized Controlled Trial.. Orthopaedic Journal of Sports Medicine, 2022. DOI: 10.1177/23259671221120678.

7. The only randomized controlled trial of alpha-2-macroglobulin for knee osteoarthritis allocated 75 patients with KL grade 2-3 disease to A2M-rich concentrate, conventionally prepared PRP, or methylprednisolone, with 12-week follow-up. The A2M group improved significantly from baseline on VAS, WOMAC, KOOS and Tegner; the PRP group improved on none; the steroid group improved on Lysholm only. Critically, the CHANGE in scores did not differ significantly between the three groups - A2M was comparable to, not better than, PRP and corticosteroid.

   Thompson K, et al. — The Effectiveness of Alpha-2-Macroglobulin Injections for Osteoarthritis of the Knee.. Bulletin of the Hospital for Joint Diseases, 2024.

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.

9. 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.