One of the most common questions I get from patients is about stem cell therapy for knees. Can it help knee arthritis and pain? Todays post is a fact-check of where things stand today in 2022 on stem cells for knee issues.

You can watch a video overview of this post on our Stem Cell YouTube Channel below.

Stem cell therapy for knees | Look at the Data |Some biased studies? |Clinical trials: no clear benefit | Cost: $5,000-$10,000 | Risks & Efficacy | 2022 and Looking Ahead | References

Quick Article Summary and Claim Review.Stem cells are a still unproven approach to knee problems like pain and arthritis, but many clinics market this approach, claiming it works and is safe. While risks appear low overall for stem cell knee injections, there have been problems on occasion. The cost of around $5,000-$10,000 at unproven stem cell clinics is not covered by insurance or Medicare. Overall, this experimental therapy may not be worth the cost and risks at this time. More data are needed from ongoing trials. Certain patients are far more likely to benefit from knee replacement instead of stem cells depending on their age and severity of disease, but joint replacement has its own risks. You should consult your doctor.

With all those patients asking about this, perhaps then its not surprising that for-profit clinics have zeroed in. One of the most common claims made by unproven, for-profit stem cell clinics is related to knees.

They sell the idea that their stem cells can help knee arthritis and associated pain, but what is the evidence to back this up? What about other products like platelet rich plasma (PRP) for knees?

There are many problems with the claims of stem cells and other regenerative products.

In many cases what is being sold as stem cells isnt even real stem cells. It often is an amniotic extract.

Such products are probably not made from actual stem cells anyway and are dead.

But what about cases where real, live stem cells are being injected every day for knee arthritis? For other kinds of joint problems? What about PRP?

Mostly the answer seems to be no, with a few maybes.

One of the challenges in this area is that there is so much noise out there. The data are a real jumble.

With just one search on PubMed I found more than 400 articles. Such articles often report conflicting big-picture findings as well.

And there are likely many more articles depending on how one does the literature search.

The first three results popping up with that search are all themselves meta analyses or reviews. I could also easily find many recent clinical trial reports. Many on the surface suggest there might a small benefit to various kinds of stem cell injections, but the studies are often too small or have other issues to be sure. One phrase in this particular study kind of sums up many others: Larger sample size and long-term follow-up are required.

I interpret that to mean that this is not ready for prime time. Its not a convincing replacement for knee joint replacement. While joint replacement has its own issues, the data indicate it gives most patients back the functionality they want.

A Cochrane review of stem cells for knees appears to be ongoing without results so far. It could have a big impact.

Another meta kind of study in the British Journal of Sports Medicine identified potential challenges to many of the regenerative studies on knees. The issue is the risk of bias in many of the stem cell for knees studies. The authors conclude:

Six trials with high risk of bias showed level-3 or level-4 evidence in favour of stem cell injections in KOA. In the absence of high-level evidence, we do not recommend stem cell therapy for KOA.

I know that stem cell clinic doctors can find plenty of studies supposedly supporting what they are offering for knees, but the question is which studies are the strongest? Also, is there some coherent signal of benefit and safety rising above the noise overall? I didnt see it.

Many universities and medical centers including the Mayo Clinic are studying stem cells for various orthopedic injuries including knee problems. These clinical trials so far have not produced clear data supporting regenerative approaches as a new standard of care.

Some reasons include that some trials to date havent been designed or powered to measure efficacy, other trials produced inconclusive results, and many trials are still ongoing. As to the first reason, an example is The completed Phase 1 Mayo Clinic trial.This study of bone marrow stem cells for knees was very preliminary.

The published Mayo study itself was direct about the inconclusive results:

Study patients experienced a similar relief of pain in both BMAC- and saline-treated arthritic knees.

In other words, the stem cells did nothing more than just an injection of salt water.

A search I did on Clinicaltrials.gov found more than 100 listings of studies of stem cells for knees. I did the search on March 29, 2021.

Other trials are examining PRP for knee issues. PRP could actually be more promising here than MSC-type cells as they are currently being used.

The CIRM Blogrecently covered the issue of stem cells for knee arthritis at clinics. In large part the post seemed inspired by a new at that time comprehensive study that sheds major doubt on this approach.

Some of the main take-homes from the study on clinics were nicely summarized by Kevin McCormack of CIRM, including on cost:

In a study presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, researchers contacted 317 clinics in the US that directly market stem cell therapies to consumers. They asked the clinics for information on the cost of the procedure and their success rate.

Only 36 clinics responded with information about success rates.

None offered any evidence based on a clinical trial that supported those claims, and there was no connection between how much they charged and how successful they claimed to be.

Patients are paying around $5K-$10K for a kind of stem cell treatment where clinics are largely claiming 70-100% success yet have little or no strong clinical trial evidence to back it up. The average cost data here fit wellwith the numbers in a poll I did on The Niche of what patients say they paid for stem cell therapies more generally. Note that this approach is not covered by insurance or Medicare.

McCormack has quotes both from the lead authors,Nicolas Piuzzi andGeorge Muschler, of the study entitled, The Stem-Cell Market for Treatment of Knee Osteoarthritis: A Patient Perspective, which is published in Journal of Knee Surgery with some big picture perspectives and thoughts on the meaning of their work. Check it out.

Basically, theres a disconnect between the state of the clinical science in this area and what is being widely marketed for profit. Im not aware of massive patient side effects in this area so safety, while not assured by any means, is perhaps not the biggest issue.

Risks. A possible risk comes from poor injection methods. I have had patients report that injections to the knee went badly after the needle ended up outside the knee joint. Some clinics using imaging to guide the process so thats a plus. Many are not. Probably the other main risk is infection. It is unclear if the stem cell materials themselves pose specific risks like incorrect tissue growth.

Efficacy. Overall, there is minimal evidence of efficacy from properly controlled studies. For instance, the authors ofthis stem cells for knees studysuggest potential benefit of bone marrow stem cells for knee arthritis, but although it did have a control group, it wasnt blinded and was underpowered.Heres a more recent, blinded studyarguing for some moderate benefit, but it was underpowered as well and no benefit was seen after 12 months. Clinics will point to yet other studies that purportedly report benefits, but the big picture is just not very clear.

I hope in the future we get that data as a field so we can have better clarity here. You can see some past posts including on knee arthritis. Its apparent that for up to 8 years or more this issue has been percolating.

Other alternatives including knee replacements, especially for older patients, can offer great outcomes. The Mayo Clinic and others are using approaches beyond stem cells. They are also testing approaches using cartilage cells called chondrocytes instead of stem cells, which also show promise.

My viewis that stem cell injections for knee arthritis from clinics directly marketing to consumers is most often going to be a big waste of money for patients and again there are risks. This is not to say that theres no hope of stem cells for arthritis or specifically for knee arthritis, but caution is in order right now on this front.

Im optimistic about the future of this area, but most of whats going on now commercially is not ready for prime time.

Disclaimer: this post is not medical advice. Consult with your doctor before making medical decisions.

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Stem cell therapy for knees: fact-check, costs, risks

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