On this page
PRP is not stem cell therapy, it is far cheaper, and in some indications it has better evidence than the cells sold alongside it. Platelet-rich plasma is worth understanding properly — partly because it may be the more sensible purchase, and partly because it is frequently sold as though it were something it is not.
What PRP actually is
Your own blood, spun in a centrifuge to concentrate the platelets, then injected. The whole process takes under an hour and happens in the same room.
Platelets carry growth factors released during normal healing, and the rationale is that concentrating them at a site of damage amplifies that process.
There are no stem cells in it, in any meaningful sense. It contains platelets, plasma, and depending on preparation a variable quantity of white and red blood cells.
That last point matters: leucocyte-rich and leucocyte-poor preparations behave differently, and studies using one do not straightforwardly support the other.
Why it gets confused with cell therapy
Both are autologous, both are injected into joints or tendons, both are described as regenerative, and both are sold by the same clinics.
The difference is substantial. PRP is a concentrate of a blood component prepared in an hour. Cell therapy involves isolating and usually culturing living cells over weeks.
Cost differs by an order of magnitude, which is the practical reason to be clear about which you are buying — see the cost page.
The confusion is sometimes deliberate and often not. Stromal vascular fraction, marrow concentrate and PRP all sit in a middle ground that gets described as regenerative therapy, and patients reasonably assume they are buying the thing the research was done on.
The evidence in knee osteoarthritis
Extensively studied, and genuinely mixed — which makes it a useful case study in reading a literature honestly.
A randomised trial compared intra-articular PRP against placebo injection, measuring pain and medial tibial cartilage volume — Effect of Intra-articular Platelet-Rich Plasma vs Placebo Injection on Pain and Medial Tibial Cartilage Volume. It is among the better-conducted studies in this field and it did not find benefit over placebo.
Set against that, meta-analyses comparing PRP with hyaluronic acid have generally favoured PRP — Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis and Platelet-rich plasma versus hyaluronic acid in the treatment of knee osteoarthritis: a meta-analysis.
And a 2025 analysis argued the improvement reaches clinical significance — PRP Injections for the Treatment of Knee Osteoarthritis: The Improvement Is Clinically Significant.
How to hold those findings together
The comparison matters enormously. PRP beating hyaluronic acid is a different claim from PRP beating saline, and the placebo-controlled trial is the harder test.
A treatment can genuinely outperform an active comparator while not outperforming placebo, if the active comparator also does little.
That is why a clinic citing only the favourable meta-analyses is presenting a selected literature — see what the evidence levels mean.
PRP against cell therapy directly
One study compared patients receiving PRP against bone marrow aspirate concentrate — Patients With Knee Osteoarthritis Who Receive Platelet-Rich Plasma or Bone Marrow Aspirate Concentrate — which is the comparison most patients actually face and which is rarely made.
Head-to-head data of that kind is worth far more than two separate literatures compared informally, because the two groups were treated in the same place, assessed the same way and followed for the same length of time. Almost nothing else in this field offers that.
See knee osteoarthritis for the cell therapy evidence in the same joint.
Where else it is used
Tendinopathy, particularly tennis elbow and patellar tendinopathy, with a literature that is similarly mixed — see tendon injury.
Hair loss and aesthetic applications, where studies are small, short and rarely blinded, and where the outcome being measured is frequently a photograph.
And in sports medicine generally, where it became popular well ahead of the evidence and has been retreating since. That trajectory — enthusiastic adoption, then contraction as better trials report — is the one worth keeping in mind for every treatment discussed on this site.
The standardisation problem
There is no standard PRP. Preparations differ in platelet concentration, whether leucocytes are included, whether platelets are activated, spin protocol and injection volume.
Two clinics both offering “PRP” may be injecting products with several-fold differences in platelet count.
This makes the literature hard to pool and makes any specific claim about PRP difficult to attach to the specific preparation you are being offered.
The practical question is which preparation a clinic uses and what platelet concentration it achieves. Very few can answer that, which tells you how closely the published protocols are being followed.
Risks and practicalities
Low risk, and that is a genuine advantage. It is your own blood, so there is no donor question and no culture step where contamination could enter.
Post-injection soreness for a few days is common and can be sharp for the first forty-eight hours, and the small infection risk of any injection applies.
It is cheap enough that trying it before committing to cell therapy is a defensible sequence — see adverse events and MSC therapy.
A reasonable order for a knee, on current evidence, is a completed exercise programme first, then PRP if that has not been enough, and only then a conversation about cells.
PRP carries most of the evidence sold under other names in aesthetics: see hair thinning and cosmetic rejuvenation.
Frequently asked questions
Is PRP a stem cell treatment?
No, and the distinction is worth insisting on. It is concentrated platelets from your own blood, spun in a centrifuge in under an hour, with no stem cells in it in any meaningful sense and no culture step at all.
Does it work for knee arthritis?
Mixed. A well-conducted placebo-controlled trial found no benefit over placebo, while meta-analyses against hyaluronic acid have generally favoured it.
Why do the studies disagree?
Largely because of what PRP was compared against. Beating hyaluronic acid is a weaker claim than beating a saline placebo.
Is it better value than cell therapy?
It costs a fraction as much and has been studied more. Whether it works better is the question one head-to-head study has actually examined.
Are all PRP preparations the same?
No, and this is a real problem. Platelet concentration, leucocyte content and protocol vary several-fold between clinics offering the same-named treatment.
Is it safe?
Relatively. It is your own blood with no culture step, so the main risks are post-injection soreness and the small infection risk of any injection.
Requesting a medical evaluation
Nothing on this page establishes whether any treatment is appropriate for you. That needs your history, your imaging and your current medications read by a clinician. If you would like that review, send your records and we will tell you honestly whether there is anything worth discussing — including when the answer is no.
This page is general information, not medical advice, and does not create a doctor–patient relationship. Regenerative treatments discussed here are in most cases investigational. Discuss any treatment with a clinician who knows your history.