Stem cells before knee replacement are often marketed as a way to regenerate cartilage, restore an arthritic joint, or avoid surgery. These claims are appealing when pain is limiting your life and total knee replacement feels like a major decision.
However, the term “stem cell treatment” can describe several different products, and what is injected may not match what the marketing suggests. Current evidence does not show that these injections reliably rebuild advanced cartilage loss or return an arthritic knee joint to its previous condition.
What does “stem cell injection” mean?
Stem cells have the ability to develop into other types of cells under specific biological conditions. Mesenchymal stromal cells, frequently called mesenchymal stem cells, have been studied because of their potential effects on inflammation, immune activity, and tissue signaling.
In clinical marketing, the term “stem cells” may refer to products prepared from bone marrow, adipose tissue, umbilical cord tissue, amniotic material, or other sources. These products are not interchangeable.
Bone marrow aspirate concentrate is collected from a person’s bone marrow and processed before injection. It contains a mixture of cells, platelets, and signaling proteins. Only a small portion of the cells are mesenchymal stromal cells. Calling the entire mixture a stem cell injection can create an inaccurate impression of what is being administered.
Other products may come from donated birth tissues or laboratory-processed cells. Their composition, processing, regulatory status, and supporting evidence may differ substantially from a same-day bone marrow procedure.
Why the label is not enough
A clinic may advertise “millions of stem cells” without clearly identifying the cell source, how the cells were counted, whether they remain viable, or whether the treatment has been evaluated in controlled clinical trials.
Before paying for a treatment, ask for the exact product name, its source, how it is processed, and whether the clinician is injecting bone marrow concentrate, adipose-derived material, cultured cells, or another biologic product.
Also ask whether the treatment is part of a registered clinical trial and what evidence supports that specific product for knee osteoarthritis. Evidence about one cell preparation cannot automatically be applied to every product marketed under the same broad label.
What current research shows
Studies of mesenchymal stromal cell injections have reported mixed results. Some trials and systematic reviews describe improvements in pain or function. Others find little or no benefit compared with placebo.
A 2024 systematic review published in the Cochrane Database of Systematic Reviews concluded that these injections probably provide little to no improvement in pain or physical function for chronic knee pain associated with osteoarthritis. The authors also found uncertainty concerning structural effects and less common complications.
Improved symptoms do not prove that cartilage has regrown or that advanced osteoarthritis has been reversed.
Other reviews have reported more favorable symptom outcomes, especially at certain doses or follow-up periods. However, differences in cell source, preparation, study design, osteoarthritis severity, comparison groups, and outcome measurements make firm conclusions difficult.
This is an active area of research. That is different from having a standardized treatment with predictable results.
Do stem cell injections regrow cartilage?
Cartilage regeneration is one of the strongest claims used to market these injections. Current clinical evidence does not show reliable restoration of substantial cartilage loss in people with advanced knee osteoarthritis.
Some studies use MRI findings, cartilage measurements, or biological markers to examine possible structural changes. Results have been inconsistent, and a change detected in a research measurement does not necessarily produce a meaningful improvement in walking, stairs, sleep, or daily activities.
Osteoarthritis also involves more than cartilage. It may include changes in bone, the joint lining, ligaments, muscles, alignment, and sensitivity of the nervous system. Regenerating a small amount of tissue would not automatically correct all the factors contributing to pain and limited function.
A treatment may still be valuable if it produces worthwhile symptom relief. That benefit should be described accurately as symptom improvement rather than proof of joint restoration.
FDA status and marketing claims
The U.S. Food and Drug Administration states that regenerative medicine therapies have not been approved for the treatment of orthopedic conditions such as osteoarthritis or knee pain. This includes products commonly marketed as stem cell treatments.
A clinic offering an injection is not proof that the product has received FDA approval for knee osteoarthritis. Statements such as “FDA registered,” “FDA compliant,” or “processed in an FDA-registered facility” do not mean the treatment itself has been approved as safe and effective for your condition.
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Questions to ask before paying for treatment
Ask what will actually be injected and where it comes from. Request the evidence for that exact product and procedure, not regenerative medicine in general.
Find out how many injections are proposed, the total cost, what improvement is realistic, and how success will be measured. Ask what happens if the first treatment does not help and whether additional injections would require additional payment.
It is also reasonable to ask whether the clinician has a financial relationship with the laboratory or company supplying the product. A clear answer does not automatically invalidate the treatment, but it gives you useful context.
Be cautious when a clinic guarantees cartilage regrowth, promises that surgery will be avoided, relies mainly on testimonials, or pressures you to pay quickly. Strong claims require strong evidence.
Risks and limitations
Potential complications depend on the product and procedure. They may include pain, bleeding, infection, inflammatory reactions, contamination, immune reactions, and complications at a bone marrow or adipose tissue collection site.
The full risk profile of some products is uncertain because preparation methods differ and long-term evidence is limited. The use of your own cells does not make every procedure risk-free.
Expense is another consideration. These treatments can cost thousands of dollars and are often not covered by insurance. A high price does not establish effectiveness, and paying out of pocket does not guarantee a clinically useful result.
How this fits into a surgical decision
Trying a biologic injection does not mean you are opposed to surgery, and deciding against one does not mean you are rushing into total knee replacement. The decision should fit your symptoms, structural findings, functional limitations, goals, finances, and surgical timeline.
If surgery may occur within the next several months, speak with your orthopedic surgeon before receiving any joint injection. Evidence about the timing of cell-based products before total knee replacement is limited, and your surgeon or hospital may require a specific interval before surgery.
Stem cell injections should not displace valuable preparation. Strengthening, building stamina, understanding the surgical process, and preparing your home can improve your starting point whether or not you choose an injection.
If total knee replacement is becoming more likely, download the free 2-Week Knee Replacement Launch Plan. You can also explore The Knee Replacement Game Plan™ for a more complete approach to preparing before surgery.
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References
- US Food and Drug Administration. Important patient and consumer information about regenerative medicine therapies. Updated June 3, 2021. Accessed August 11, 2026.
- Sadeghirad B, Morgan RL, Zeraatkar D, et al. Mesenchymal stem cells for chronic knee pain secondary to osteoarthritis. Cochrane Database Syst Rev. 2024;5(5):CD013342. doi:10.1002/14651858.CD013342.pub2
- Dai W, Leng X, Wang J, Shi Z, Cheng J, Hu X, Ao Y. Intra-articular mesenchymal stromal cell injections are no different from placebo in the treatment of knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. Arthroscopy. 2021;37(1):340-358. doi:10.1016/j.arthro.2020.10.016
- Wei ZJ, Wang QQ, Cui ZG, Inadera H, Jiang X, Wu CA. Which is the most effective one in knee osteoarthritis treatment from mesenchymal stem cells obtained from different sources? A systematic review with conventional and network meta-analyses of randomized controlled trials. Ann Transl Med. 2021;9(6):452. doi:10.21037/atm-20-5116
- Tian X, Gao X, Zhang Y, et al. Relative efficacy and safety of mesenchymal stem cells for knee osteoarthritis: a systematic review and network meta-analysis. J Orthop Surg Res. 2024;19(1):405. doi:10.1186/s13018-024-04884-7
Educational Disclaimer: This article provides general educational information and is not medical advice. It does not determine whether a cell-based injection is appropriate for a specific person, diagnose the source of symptoms, or replace guidance from a surgeon, physician, physical therapist, or other licensed healthcare professional. Treatment decisions and timing before surgery must be individualized.