Knee pain from osteoarthritis is one of the most common reasons patients ask about stem cell therapy for knees. Many have tried painkillers, physiotherapy and injections, and want to avoid or delay knee replacement surgery. This guide explains what a stem cell knee injection is, what the research really shows, who may be a good candidate, what it may cost, and which questions to ask before choosing a clinic.
Arabic readers: see our article on stem cells for joints and bones (in Arabic).
What is stem cell therapy for knees?
In knee osteoarthritis, the cartilage that covers the ends of the bones slowly wears down. Because cartilage has almost no blood supply, it has very limited ability to repair itself. The result is pain, stiffness, swelling and reduced mobility.
A stem cell knee injection places cells directly into the knee joint. The most studied cells are mesenchymal stem cells (MSCs), obtained from bone marrow, fat tissue or the umbilical cord. Current research suggests they work mainly by releasing signals that reduce inflammation and support the cells already in the joint, rather than by simply "growing new cartilage".
Types of regenerative knee injections
Culture-expanded mesenchymal stem cells: cells are prepared and multiplied in a specialized laboratory, then tested before use. This allows a defined cell dose.
Bone marrow aspirate concentrate (BMAC): bone marrow is taken from the patient and concentrated on the same day. It contains a small number of stem cells together with other cells and growth factors.
Fat-derived cell preparations: cells obtained from the patient's own fat tissue by a small liposuction.
Platelet-rich plasma (PRP): often marketed alongside stem cells, but PRP does not contain stem cells. It is a concentrate of platelets and growth factors from the patient's blood.
Does stem cell therapy for knees work? What the evidence shows
Knee osteoarthritis is the condition with the largest number of randomized controlled trials on stem cell therapy. A 2025 meta-analysis of six randomized trials, including around 300 patients, found that a single intra-articular injection of mesenchymal stem cells significantly improved pain and function at 12 months, with mostly mild, short-term side effects such as temporary joint swelling.
There are three important points every patient should understand:
The overall quality of evidence is still moderate to low. Most trials are small and use different cell types, doses and methods.
Cartilage regrowth has not been consistently proven. Some studies show improvement or stabilization on MRI, others show no clear structural change.
The placebo effect in knee pain is large. This is why only controlled studies can show whether a treatment truly works.
In terms of regulatory approval, one umbilical cord blood-derived cell product (Cartistem) has been approved in South Korea since 2012 for cartilage repair. In the United States and the European Union, no stem cell therapy is currently approved by the FDA or the EMA for knee osteoarthritis. In the EU, such treatments are offered within clinical studies or individual programs under specific regulations for advanced therapies.
Success rate of stem cell therapy for knees: what affects results
There is no single, official success rate, and you should be cautious with any clinic that quotes one. In randomized trials, "success" is usually measured as a meaningful reduction in pain and improvement in function on standard scores, such as WOMAC or VAS, after 6 to 12 months. On average, patients treated with mesenchymal stem cells improved more than those in control groups, but not every patient responded.
Results tend to be better in:
Mild to moderate osteoarthritis (Kellgren–Lawrence grade 2–3), rather than advanced "bone-on-bone" disease
Patients with good leg alignment and no major untreated meniscus or ligament injury
Patients who combine treatment with weight management and physiotherapy
A realistic goal is less pain, better mobility and possibly delaying knee replacement, not a new knee.
Who may be a good candidate?
Most studies included patients with mild to moderate knee osteoarthritis. Factors your doctor will consider include:
The stage of arthritis on X-ray and MRI
Your age, weight and activity level
Previous treatments and how you responded
Leg alignment and other knee injuries, such as meniscus or ligament tears
Other conditions such as diabetes or autoimmune diseases
In very advanced, "bone-on-bone" osteoarthritis, knee replacement is often still the most effective option. A responsible clinic will tell you this honestly.
Stem cell therapy vs knee replacement
Knee replacement is a well-established operation with predictable results for advanced arthritis, but it involves major surgery, hospital stay and months of rehabilitation.
A stem cell knee injection is minimally invasive, with a short recovery, but results vary and the long-term effect is still being studied. It is mainly considered in earlier stages, or by patients who want to delay surgery.
The two are not direct competitors. The right choice depends on the stage of your arthritis and your goals, which is why an individual medical review comes first.
What happens during treatment?
1. Medical review: your doctor reviews your X-ray or MRI, symptoms and medical history.
2. Preparation: depending on the method, cells are prepared in a laboratory or collected on the day of treatment.
3. Injection: the cells are injected into the knee joint under sterile conditions, often guided by ultrasound.
4. Recovery: most patients walk the same day. Temporary swelling or discomfort for a few days is common.
5. Follow-up: improvement, if it occurs, usually develops gradually over weeks to months. Results are typically assessed at 6 and 12 months.
How much does stem cell therapy for knees cost?
The cost of a stem cell knee injection varies widely between clinics and countries. The main factors are:
The type and source of cells and how they are prepared and tested
The cell dose and the number of knees treated
Imaging, pre-treatment tests and follow-up
Travel and accommodation if you are treated abroad
Most health insurers, including US insurers, do not cover stem cell therapy for knees because it is not yet part of standard approved care. Be cautious with clinics that quote a fixed price before seeing your X-rays or MRI.
Risks and side effects
In controlled studies, knee injections of mesenchymal stem cells have generally shown a good safety profile. The most common side effects are temporary pain and swelling in the joint. Serious complications such as joint infection are rare but possible, which is why sterile technique, laboratory quality and medical supervision are essential.
Questions to ask any clinic
Which type of cells will be used, and in which laboratory are they prepared and tested?
How many cells will be injected, and why this dose?
Which published studies support this treatment for my stage of arthritis?
What results are realistic for me, and what cannot be promised?
Would knee replacement or another treatment be a better option in my case?
How is follow-up organized after treatment?
Frequently asked questions
Can stem cells regrow knee cartilage?
This has not been consistently proven. The realistic goal is to reduce pain and improve function, and possibly slow the progression of arthritis in some patients.
How long does a stem cell knee injection last?
In published studies, benefits are usually measured at 6 to 12 months, and some studies report longer effects. Long-term data beyond a few years are still limited.
What is the success rate of stem cell therapy for knees?
There is no single success rate. Results depend on the stage of arthritis, the cell type and dose, and the patient. Trials show average improvements in pain and function, but not every patient responds.
Is stem cell therapy for knees FDA approved?
No. Currently no stem cell therapy is FDA-approved for knee osteoarthritis. The same is true in the EU, where such treatments are offered within regulated research or individual treatment programs.
Is it better than PRP or hyaluronic acid injections?
Some trials suggest MSC injections may give larger improvements than hyaluronic acid, but direct comparisons are limited and results vary. Your doctor can explain which option fits your situation.
Stem cell knee treatment at Regenova BioTech
Regenova BioTech is a regenerative medicine clinic in Sofia, Bulgaria, inside the European Union, working with a specialized laboratory partner in Graz, Austria. Every program starts with a free review of your knee X-ray or MRI, not a sales offer. If knee replacement or another option is better for you, we tell you. Patients from the United States can read our guide for US patients, and you can see all conditions we assess. If you are considering treatment abroad, read our patient guide to stem cell therapy in Bulgaria, which explains EU regulation, safety and how to choose a clinic.
Send your knee imaging and medical reports for a free, no-obligation review via WhatsApp at +49 176 5689 1000 or through our contact form.
This article is for general information and does not replace individual medical advice. Medically reviewed by Dr. Younis Yaseen, Medical Director, Regenova BioTech.
References
Rahmadian R, et al. Efficacy of a single intra-articular injection of mesenchymal stem cells for knee osteoarthritis: a dose-focused meta-analysis of randomized controlled trials. J Orthop Surg Res. 2025;20:812.
Contextual effects of mesenchymal stem cell injections for knee osteoarthritis: systematic review and meta-analysis of randomized controlled trials. PMC12487426.
Regulation (EC) No 1394/2007 on advanced therapy medicinal products.
