What stem cells are
A stem cell is a cell that can renew itself and develop into more specialized cells. Researchers group them by how many cell types they can become:
- Embryonic stem cells come from a very early embryo and can become any cell type in the body. That range is also their main risk, because undifferentiated cells can form tumors.
- Adult (tissue) stem cells live in bone marrow, blood, fat, and other tissues, where they maintain and repair the tissue around them. Their range is narrower.
- Mesenchymal stromal cells, often called MSCs, are the adult cells found in bone marrow and fat that can give rise to bone and cartilage. These are the cells most orthopedic treatments aim to use.
- Induced pluripotent stem cells are adult cells reprogrammed in a lab to behave like embryonic stem cells. They are used in research and early clinical trials.
- Perinatal cells come from umbilical cord blood, cord tissue, placenta, or amniotic tissue collected after birth.
What stem cell therapy means in practice
"Stem cell therapy" covers very different treatments. The table below separates the established medical use from the treatments most people see advertised.
| Type | Where the cells come from | Used for | Status and evidence |
|---|---|---|---|
| Blood stem cell transplant | Bone marrow, blood, or umbilical cord blood from you or a donor | Leukemia, lymphoma, myeloma, and some blood and immune disorders | Established treatment with decades of data; cord blood products are FDA-approved |
| Bone marrow concentrate (BMAC) | Your own marrow, drawn from the hip and concentrated the same day | Knee arthritis, tendon, ligament, and cartilage problems | Not FDA-approved for any orthopedic condition; pain improves in studies, but it has not beaten other injections |
| Fat-derived cells | Your own fat, collected by a small liposuction and processed | Knee arthritis and other joint pain | Not FDA-approved for orthopedic use; no better than a steroid injection at one year in a large trial |
| Donor birth-tissue products | Umbilical cord, placental, or amniotic tissue from a donor | Joint pain, wounds, and many marketed uses | Not FDA-approved for orthopedic use; quality and contents vary between products |
According to the FDA, the only stem cell products approved in the United States are blood-forming stem cells from umbilical cord blood, used for disorders of blood production. Bone marrow and blood stem cell transplants, a long-standing hospital treatment, sit in the same family. Everything in the lower three rows is a newer, still-evolving use.
How stem cell therapy works
Blood stem cell transplants
In a transplant for leukemia or another blood cancer, chemotherapy or radiation destroys the diseased marrow, and healthy stem cells from the patient or a donor are infused into a vein. Those cells settle in the marrow and rebuild the blood and immune system. The infusion takes a few hours, and recovery takes weeks of close monitoring.
Orthopedic injections
In sports and regenerative medicine, the goal is to support repair in a painful joint, tendon, or ligament. The cells are thought to work mostly through the signals they release, which can calm inflammation and recruit the body's own repair processes, more than by turning into new cartilage. A typical procedure with your own cells looks like this:
- An evaluation of the diagnosis, imaging, and prior treatment
- Collection of bone marrow from the back of the hip, or fat from the abdomen or flank, under local anesthetic
- Processing to concentrate the cells, usually while you wait
- An injection placed with ultrasound or fluoroscopy guidance
- A rehab plan and follow-up over the following weeks and months
The most common version uses bone marrow. Read What is bone marrow aspirate concentrate (BMAC)? for a step-by-step look at that procedure.
What stem cell therapy is used for
Medicare's national coverage policy lists the established uses of blood stem cell transplantation, including leukemia, aplastic anemia, multiple myeloma, certain lymphomas, and inherited immune disorders such as severe combined immunodeficiency.
In orthopedics and sports medicine, cell-based injections are used, off-label, for:
- Knee, hip, and shoulder osteoarthritis
- Partial tendon and ligament tears that have not healed with rehab
- Focal cartilage injuries, sometimes alongside surgery
- Problems that have not responded to PRP or other injections
Be cautious of any clinic that offers one stem cell treatment for a long list of unrelated conditions, such as autism, Parkinson's disease, lung disease, and joint pain. The FDA has not approved stem cell products for any of those uses.
Does stem cell therapy work?
For blood cancers and blood disorders, transplants are a proven, lifesaving treatment. For joint pain, the honest answer is that many patients improve, but the treatment has not yet shown that it works better than simpler options.
- In a 2023 randomized trial of 480 patients with knee osteoarthritis, injections of bone marrow concentrate, fat-derived cells, and umbilical cord tissue cells all reduced pain. None was superior to the others or to a steroid injection at one year, and MRI showed no change in the joint.
- A 2024 review of eight randomized trials found that bone marrow concentrate improved pain and function from about one month after injection. Compared with hyaluronic acid, PRP, and other injections, it showed no clinically meaningful advantage.
Injections can ease pain and support healing in the right patient. They do not regrow a worn-out joint, and they are no substitute for surgery when surgery is clearly the better option.
Is stem cell therapy safe?
The answer depends on the product and who delivers it. In clinical trials of knee injections using a patient's own bone marrow concentrate, serious complications were rare. A 2024 analysis of six randomized trials found complication rates similar to other knee injections, with joint swelling the most common, in about 18% of patients. Soreness at the collection site and the injected area for several days is expected.
The FDA has received reports of serious harm from unapproved products, including:
- Blindness
- Reactions at the collection or injection site
- Tumor formation and cells growing into unwanted tissue
- Bacterial infections, including life-threatening bloodstream infections
- Products contaminated during processing or not tested for diseases such as hepatitis and HIV
- Delayed treatment when a proven option was available
Your own cells, processed the same day under sterile conditions and placed with imaging guidance, carry a different risk profile from a donor product of unknown origin.
Is stem cell therapy legal in the US and Florida?
Under federal law, most stem cell and other regenerative products must go through FDA approval, or an FDA-overseen clinical trial, before they can be marketed. The FDA warns that charging for an unapproved product outside a clinical trial can be a sign of an illegal offer. Some procedures that return a patient's own minimally processed tissue in the same visit, such as bone marrow concentrate, are regulated under separate rules.
Florida went further. A law that took effect on July 1, 2025 (Chapter 2025-185, from Senate Bill 1768) lets physicians use stem cell therapies that are not FDA-approved when the treatment relates to orthopedics, wound care, or pain management and falls within the physician's scope of practice. The conditions include:
- The cells must come from a facility registered with the FDA and accredited by a recognized organization, such as the National Marrow Donor Program or the American Association of Tissue Banks.
- The product must contain live cells, confirmed by a viability report sent to the physician before use.
- The facility must follow federal current good manufacturing practices.
- Every advertisement must state that the therapy is not FDA-approved, and the patient must sign a consent form covering the treatment, its risks, expected results, and alternatives.
- Cells derived from a fetus or embryo after an abortion are prohibited.
Is stem cell therapy covered by insurance?
Medicare and private insurers cover blood stem cell transplants for approved indications. Orthopedic stem cell injections, including bone marrow concentrate and fat-derived cells, are generally not covered by Medicare or commercial plans, so patients pay out of pocket. Some plans may still cover the consultation, X-rays, or MRI that come before a procedure.
How much does stem cell therapy cost?
Prices vary widely. A 2017 study in which researchers called U.S. stem cell clinics as a simulated patient found an average price of $5,156 for a single-knee injection. The same clinics claimed that about 82% of patients improved, a figure well above what published research supports. What drives the price:
- The cell source: your own bone marrow or fat, or a donor product
- How the cells are processed and concentrated
- Whether ultrasound or fluoroscopy guides the injection
- The number of joints or areas treated in one session
- Whether PRP or other injections are added
- Follow-up visits and rehab included in the quote
How long does stem cell therapy last?
Improvement after an orthopedic injection usually builds over weeks to a few months. Most randomized trials follow patients for 12 to 24 months, and one followed them for four years. Many report pain relief across that period, but long-term durability is not established, and the best number and timing of repeat injections is still unknown. Milder arthritis tends to respond better than bone-on-bone disease, and rehab, strength, and body weight all influence how long the benefit holds.
Questions to ask any clinic
- Where do the cells come from, and how are they processed?
- Is the product FDA-approved, part of a clinical trial, or offered under Florida law?
- What does the published evidence show for my specific diagnosis?
- Who performs the procedure, and is it image-guided?
- What are the risks, and what are my alternatives, including doing nothing?
- What is the full cost, and what does rehab look like afterward?
Stem cell therapy in Miami
I am a sports medicine physician, board-certified by the American Board of Family Medicine, and I evaluate joint, tendon, and ligament problems in Miami. For many patients the right first step is rehab, a targeted injection, or PRP therapy. When a procedure using your own bone marrow makes sense, I will explain what the evidence shows for your diagnosis and what a realistic result looks like. Read more about stem cell therapy in Miami, or book a consultation.
Frequently asked questions
What is stem cell therapy used for?
The proven use is blood stem cell transplantation for leukemia, lymphoma, multiple myeloma, aplastic anemia, and certain inherited immune disorders. In sports and regenerative medicine, a patient's own bone marrow or fat cells are injected for knee arthritis and some tendon, ligament, and cartilage problems. Those orthopedic uses are not FDA-approved, and the evidence for them is still developing.
How does stem cell therapy work?
In a blood stem cell transplant, high-dose treatment clears the diseased marrow and the transplanted stem cells rebuild a healthy blood and immune system. In orthopedic injections, the cells appear to work mostly by releasing signals that calm inflammation and support the tissue's own repair. Injections do not regrow a worn-out joint.
Does stem cell therapy work?
For blood cancers and some blood disorders, stem cell transplants are an established, lifesaving treatment. For knee arthritis, many patients report less pain and better function, but in a 480-patient randomized trial published in 2023, bone marrow, fat, and umbilical cord cell injections were no better than a steroid injection at one year. Results depend heavily on the diagnosis and its severity.
Is stem cell therapy legal in the US?
Yes, in specific forms. FDA-approved blood stem cell products and transplants are legal, and some same-day procedures using a patient's own minimally processed tissue fall under separate federal rules. Most other stem cell products need FDA approval before they can be marketed, and Florida has allowed certain unapproved stem cell therapies in orthopedics, wound care, and pain management since July 1, 2025, under strict conditions.
Is stem cell therapy covered by insurance or Medicare?
Insurance and Medicare cover blood stem cell transplants for approved indications such as leukemia and multiple myeloma. Orthopedic stem cell injections, including bone marrow concentrate, are generally not covered, so patients usually pay out of pocket. Some plans may still cover the office visit or imaging that comes before a procedure.
How much does stem cell therapy cost?
A survey of U.S. clinics published in 2017 found an average price of $5,156 for a single-knee stem cell injection. Cost depends on the cell source, how the cells are processed, whether imaging guidance is used, how many areas are treated, and what follow-up is included. Ask any clinic for an itemized, all-in quote before you commit.
Is stem cell therapy safe?
Injections of a patient's own bone marrow concentrate have a low rate of serious complications in clinical trials, and temporary pain and swelling are the most common side effects. The FDA has documented serious harm from unapproved products, including blindness, tumor formation, and life-threatening infections. Safety depends on the product, how it is prepared, where it is injected, and who performs the procedure.
How long does stem cell therapy last?
Most controlled trials of orthopedic stem cell injections follow patients for one to two years, and improvement has been reported throughout that window in many studies. Longer-term durability is not well established, and the ideal number and timing of repeat injections has not been worked out. Activity, weight, rehab, and the severity of the underlying problem all affect how long relief lasts.
Sources
- FDA: Important patient and consumer information about regenerative medicine therapies
- University of Washington ISCRM: How does stem cell therapy work?
- EuroStemCell: What are stem cell treatments?
- Biehl JK, Russell B. Introduction to stem cell therapy. J Cardiovasc Nurs. 2009
- Mautner K, et al. Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial. Nat Med. 2023
- Han JH, et al. Bone marrow aspirate concentrate injections for the treatment of knee osteoarthritis: a systematic review of randomized controlled trials. Orthop J Sports Med. 2024
- Kim GB, et al. Bone marrow aspirate concentrate: its uses in osteoarthritis. Int J Mol Sci. 2020
- Fucaloro S, et al. Complication rates of bone marrow aspirate concentrate injections versus other injectable therapies for knee osteoarthritis. J Orthop. 2024
- Piuzzi NS, et al. The stem-cell market for the treatment of knee osteoarthritis: a patient perspective. J Knee Surg. 2018
- CMS: National Coverage Determination 110.23, Stem Cell Transplantation
- Florida Senate: SB 1768 (2025), Stem Cell Therapy
- Laws of Florida: Chapter 2025-185