Quick answer, as of October 2026: Stem cell knee injections are widely advertised, but a large trial found they worked no better than a steroid injection. A 2023 randomised trial of 480 people in Nature Medicine tested bone marrow, fat-derived and umbilical cord cell injections and found none was superior at 12 months. PRP has been studied in more trials and needs a blood draw rather than a marrow harvest, but benefits vary and cartilage regrowth is not established.
Are stem cell knee injections better than PRP?
- In the UK, therapies made from processed cells are regulated by the MHRA as advanced therapy medicinal products, so many treatments marketed abroad as stem cell cures are not available here.
- A 2023 phase 3 trial of 480 people in Nature Medicine found no cell-based injection was superior to a steroid injection for knee arthritis pain at 12 months.
- The same trial found no change in knee structure on MRI with any of the cell treatments.
- A 2020 randomised trial of 90 people found bone marrow concentrate and PRP both improved symptoms, with no significant difference between groups at one year.
- The London PRP Clinic by The Wellness offers doctor-led knee PRP from £750, with a free doctor review on WhatsApp.
What is a stem cell knee injection?
A stem cell knee injection usually means an injection of cells taken from bone marrow, fat or donated umbilical cord tissue. Same-day concentrates are mixed-cell preparations and should not be assumed to contain a proven therapeutic dose of stem cells. Researchers increasingly call them cell-based or orthobiologic injections rather than stem cell treatments.
Products studied in trials include the following.
- Bone marrow aspirate concentrate. Bone marrow is drawn from the pelvis under local anaesthetic, concentrated and injected into the knee.
- Fat-derived cells. Fat is taken by mini liposuction, processed and injected.
- Umbilical cord cells. Cells from donated umbilical cord tissue are grown in a laboratory and injected.
Ask a doctor about your knee options on WhatsApp and include any X-ray or scan reports.
Are stem cell injections legal in the UK?
Stem cell treatments in the UK are tightly regulated. Therapies made from cells that have been substantially processed or grown in a laboratory are classed as advanced therapy medicinal products and regulated by the Medicines and Healthcare products Regulatory Agency. ATMPs placed on the UK market need a marketing authorisation. Unlicensed supply can also take place under restricted hospital-exemption or specials routes, with manufacturer licensing requirements. The exact product and route must be checked, not inferred from the phrase "stem cells".
Some same-day, minimally processed preparations may be regulated differently; the product and process determine the route. People should be cautious of clinics, in the UK or abroad, that promise to regrow cartilage or cure arthritis with stem cells. Ask what exactly is being injected, how it is regulated and what evidence supports it.
Do stem cell knee injections work?
Results depend on the exact preparation. A large direct comparison did not establish better outcomes than a steroid injection. The MILES trial, published in Nature Medicine in 2023, randomised 480 adults with knee osteoarthritis (440 were in the primary analysis) to bone marrow concentrate, umbilical cord cells, stromal vascular fraction or a steroid injection.
Every group improved meaningfully in pain at 12 months, including the steroid group. None of the cell-based injections was superior to the others or to the steroid, and none changed knee structure on MRI. The authors concluded that the trial showed no superiority of any cell therapy over steroid.
How does PRP compare with stem cell injections?
PRP avoids marrow harvest or liposuction. It can be discussed as a symptom-management option alongside exercise, physiotherapy and other suitable treatments. A 2020 randomised trial of 90 people in the Orthopaedic Journal of Sports Medicine found bone marrow concentrate and PRP both improved symptoms, with no significant difference between groups for knee arthritis at one year.
PRP has been tested in many more randomised trials. A 2025 meta-analysis by Bensa and colleagues pooled 18 randomised trials and 1,995 people. It found clinically relevant improvement in WOMAC function scores over placebo at 1, 3, 6 and 12 months, and clinically relevant pain relief at 3 and 6 months. Platelet concentration influenced results. These are pooled effects, not a promise of an individual response.
Stem cell injections and PRP at a glance
- Source. Cell injections use bone marrow, fat or donor cord tissue. PRP uses a simple blood sample.
- Procedure. Cell injections need a bone marrow draw or liposuction. PRP requires a blood draw and a knee injection.
- Evidence. Cell injections were not superior to steroid in a 480-patient trial. PRP is supported by multiple meta-analyses of randomised trials.
- Regulation. Laboratory-grown cell products are regulated as medicines. PRP is prepared from your own blood during the same appointment.
- Recovery. Cell injections can leave soreness at the harvest site. PRP can cause a temporary flare, with recovery varying between people.
Book your free suitability review on WhatsApp for an honest comparison for your knee.
What are the limits of the PRP evidence?
The NICE guidance now numbered HTG497 raises no major safety concerns but says efficacy evidence is limited in quality. It calls for special arrangements for governance, consent and audit or research. The recommendations have not changed with the new number.
The 2021 RESTORE trial in JAMA found no significant benefit over saline in 288 people for pain or medial tibial cartilage volume at 12 months. This matters alongside positive meta-analyses: preparation, selection and study design differ. PRP is a possible symptom-management option, not a cure or a proven way to regrow cartilage.
Who is a good candidate for PRP instead of stem cells?
PRP may be considered after assessment for some people with mild to moderate knee osteoarthritis. Exercise and other established care remain important. Typical features include the following.
- Knee pain and stiffness with X-ray or scan findings of mild to moderate arthritis.
- Limited improvement with exercise, physiotherapy and weight management.
- A wish to avoid surgery, a bone marrow draw or liposuction.
- No active infection or platelet disorder.
Severe symptoms or advanced joint damage need a wider treatment discussion, which can include a surgical opinion.
What questions should I ask any regenerative clinic?
Asking the right questions protects people considering any regenerative injection. Ask each clinic the following.
- What exactly will be injected, and how is it prepared?
- How is the product regulated in the UK?
- Which randomised trials support this treatment for my condition?
- Who performs the procedure, and are they GMC-registered?
- What is the total cost, including any harvest procedure and follow-up?
Put these questions to our doctors on WhatsApp before you decide.
How much does knee PRP cost in London?
As of October 2026, The London PRP Clinic by The Wellness offers doctor-led knee PRP from £750. The doctor confirms the full plan and cost before treatment begins. Read our full guide to PRP joint injection costs in London.
How does the free suitability review work?
The free suitability review is a doctor's honest opinion before any appointment. Send a short description of your knee, any treatments you are considering and any X-ray or scan reports through WhatsApp. A GMC-registered doctor reviews the case and either approves you for a consultation or recommends a more suitable route.
Start your free knee review now, call +44 20 3951 3429, or email team@thewellnesslondon.com.
Frequently asked questions
Do stem cell knee injections work?
A 2023 trial of 480 people in Nature Medicine found no cell-based knee injection was superior to a steroid injection at 12 months, and none changed knee structure on MRI.
Are stem cell injections available in the UK?
Laboratory-grown cell therapies are regulated by the MHRA as advanced therapy medicinal products. Marketing authorisation, clinical-trial and restricted unlicensed routes have different requirements. Some same-day preparations are offered privately, but their regulatory status depends on the product and process.
Is PRP as good as stem cells for the knee?
A 2020 randomised trial of 90 people found bone marrow concentrate and PRP both improved symptoms, with no significant difference between groups at one year. PRP is supported by more randomised trials and uses a simpler procedure.
Can stem cells regrow knee cartilage?
Cartilage regrowth should not be promised. The 2023 MILES trial found no change in knee structure on MRI with any cell treatment.
Where can I have knee PRP in London?
The London PRP Clinic by The Wellness offers doctor-led knee PRP from £750 in London.
How can I arrange a knee assessment?
The London PRP Clinic by The Wellness is a doctor-led regenerative medicine clinic in London. The clinic offers PRP for joints, tendons, hair and skin, with every treatment planned and performed by GMC-registered doctors. Any imaging, blood tests and other services are discussed and priced before booking.
What does the British Orthopaedic Association say?
The BOA information document warns that the term "stem cells" can mislead when used for same-day concentrates. It separates these preparations from cultured cells, and does not treat cartilage regeneration as an established outcome. Ask for evidence about the exact product being offered and your grade of arthritis, rather than evidence from a different cell product.
References
- Mautner K and colleagues. Cell-based versus corticosteroid injections for knee pain in osteoarthritis, a randomized phase 3 trial. Nature Medicine, 2023.
- Anz AW and colleagues. Bone marrow aspirate concentrate is equivalent to platelet-rich plasma for the treatment of knee osteoarthritis at 1 year, a prospective randomized trial. Orthopaedic Journal of Sports Medicine, 2020.
- Bensa A and colleagues. Platelet-rich plasma versus placebo for knee osteoarthritis, meta-analysis. American Journal of Sports Medicine, 2025.
Reviewed by The Wellness Clinical Team. Updated 22 October 2026.
MHRA: advanced therapy medicinal products, regulation and licensing.
