Stem Cell Injections for Joint Pain: What They Are and What the Research Shows

What counts as a "stem cell" injection?

Stem cells are specialized precursor cells that can replace aged or damaged cells and help keep tissue healthy⁴. The same words are used for products that come from different places and are made in different ways. The main groups are:

• Bone marrow. Your own marrow is drawn, concentrated and injected. This is bone marrow aspirate concentrate, or BMAC, one of the autologous (from your own body) orthobiologics³. Our guide to BMAC covers it in detail.
• Fat (adipose tissue). Cells come from your own fat. Research describes adipose-derived mesenchymal stem cells and stromal vascular fraction (SVF)².
• Umbilical cord, Wharton's jelly and amniotic products. These come from donated birth tissue, not from you^1,3,5. Companies have made umbilical cord products available to doctors with claims of "stem cell" healing³.

Because these products come from different sources and are prepared in different ways, research on one does not automatically apply to another.

At our practice, BMAC uses your own marrow, which is drawn, processed and delivered in one visit at Pueblo Surgery Center, a free-standing, AAAHC-accredited outpatient facility.

The International Society for Stem Cell Research (ISSCR) describes stem cells as having tremendous promise for treating a range of diseases, injuries and other health conditions. It notes that some bone, skin and eye injuries are already treated by grafting tissue, with healing that relies on the stem cells within that tissue, and that important clinical trials with stem cells are underway for many other conditions⁶.

How does your own bone marrow compare with donor products?

Laboratory studies have measured what is actually in these products.

• In a 2021 study, bone marrow concentrate prepared from the marrow of middle-aged adults had more than 95% living cells, over 300 million in all. Five commercial umbilical cord products that claimed to contain "stem cells" all had some living cells, but a lower share of them (from 1% to 59%, depending on the product), and none contained the colony-forming cells that researchers usually mean by stem cells³.
• A second 2021 study examined nine commercial products made from amnion, chorion, umbilical cord and amniotic fluid. It identified 919 proteins across the products, and no live cells in any of them⁵.

Both studies found potentially useful proteins in the donor products. Some umbilical cord tissue products held higher levels of certain growth factors and cytokines, including an anti-inflammatory protein called interleukin-1 receptor antagonist, than blood and bone marrow plasma did³. In the amniotic products, the authors identified proteins that might explain their beneficial effects⁵.

What does the research show for knee arthritis?

The Cochrane review. A 2025 Cochrane review found 25 randomized trials with 1,341 participants, whose average ages ranged from 51 to 66⁴. The review found that stem cell injections may improve pain and function for up to six months after treatment⁴.

Cells from your own fat. A meta-analysis of five randomized trials looked at adipose-derived stem cells or SVF injected on their own. Compared with the control injections, which included hyaluronic acid, the cells gave significantly better pain relief and function at both 6 and 12 months. Knee pain or swelling from the procedure was no different from the control injections, and no serious side effects linked to the cells were reported. Three of the included studies reported significantly improved cartilage status on MRI after the injection. The authors described the results as remarkable clinical efficacy and safety in the short term².

Bone marrow. Our BMAC guide covers the research on bone marrow concentrate for knee and hip arthritis and for worn spinal discs.

Are stem cell injections safe?

In the Cochrane review, serious adverse events were infrequently reported, and no participants were reported to have withdrawn because of side effects⁴. As with any injection into a joint, there is a small risk of joint infection (septic arthritis)⁴. In the fat-derived cell trials, no serious side effects linked to the cells were reported².

Cells that are removed from the body and put back need careful handling. ISSCR points out that any time cells are removed, there is a risk they may be contaminated before they are reintroduced⁶.

How much do stem cell injections cost?

Researchers posing as a 57-year-old man with knee arthritis contacted 273 US centers offering stem cell therapy. Among centers that quoted a price, the average for a single-knee injection was $5,156, or about $5,000, and centers often charged patients out of pocket⁷. These are national figures from that study, not our fees. At our practice, whether you are a candidate is decided at a consultation, before any financial commitment.

How to choose a stem cell clinic

A few points help when comparing clinics:

• Know what is in the syringe. Ask whether the product comes from your own marrow or fat, or from donor tissue. Lab testing has found large differences in living cells between bone marrow concentrate and commercial donor products^3,5.
• A treatment matched to your condition. ISSCR advises extreme caution with clinics that offer the same cell treatment for a wide variety of conditions or diseases⁶.
• A clear explanation of risks. ISSCR advises being wary of any clinic that glosses over or minimizes the risks of its treatments⁶.
• A proper examination first. In our view, an injection should be offered only after someone has examined you and reviewed your imaging.

Useful questions to ask any clinic: What exactly is in the syringe, and where did it come from? What research supports it for my condition? What does the total cost include?

Who may be a candidate?

At our practice, physical therapy and viscosupplementation come first. When they have not worked, PRP, BMAC or the two combined may be considered. Not every patient is a candidate, and a proper orthopedic evaluation is essential. Candidacy is decided at a consultation, before any financial commitment, and no injection can promise a result.

If you are in the Santa Barbara area, Dr. Scheinberg can examine the joint, review any imaging and talk through the options, including whether an injection makes sense at all. Read about joint preservation or call (805) 682-1394.

References

1. 1. U.S. Food and Drug Administration. Important patient and consumer information about regenerative medicine therapies. FDA.gov, content current as of April 8, 2024. www.fda.gov
2. 2. Kim KI, Kim MS, Kim JH. Intra-articular injection of autologous adipose-derived stem cells or stromal vascular fractions: are they effective for patients with knee osteoarthritis? A systematic review with meta-analysis of randomized controlled trials. Am J Sports Med. 2023;51(3):837-848. PubMed
3. 3. Berger DR, Centeno CJ, Kisiday JD, et al. Colony forming potential and protein composition of commercial umbilical cord allograft products in comparison with autologous orthobiologics. Am J Sports Med. 2021;49(12):3404-3413. PubMed
4. 4. Whittle SL, Johnston RV, McDonald S, et al. Stem cell injections for osteoarthritis of the knee. Cochrane Database Syst Rev. 2025;4(4):CD013342. PubMed
5. 5. Becktell L, Matuska AM, Hon S, et al. Proteomic analysis and cell viability of nine amnion, chorion, umbilical cord, and amniotic fluid-derived products. Cartilage. 2021;13(2 suppl):495S-507S. PubMed
6. 6. Prutton K. 9 things to know about stem cell treatments. A Closer Look at Stem Cells, International Society for Stem Cell Research, Sep 20, 2023. www.closerlookatstemcells.org
7. 7. Piuzzi NS, Ng M, Chughtai M, et al. The stem-cell market for the treatment of knee osteoarthritis: a patient perspective. J Knee Surg. 2018;31(6):551-556. PubMed

Reviewed by Dr. Richard Scheinberg, MD, a board-certified orthopedic surgeon in Santa Barbara with 40 years of surgical experience.