What Is Stem Cell Therapy? Types, Uses, and How It Differs from Conventional Care

Stem cell therapy means treating disease with living cells, taken from your own body or from a donor. In the United States, the FDA-approved stem cell treatments are for blood cancers and other blood and immune disorders, plus one donor product for a transplant complication. None is approved for joint, spine, tendon or sports injuries.

The same two words cover both a proven hospital treatment and an unproven clinic injection. Most of what a patient needs to understand follows from keeping those two apart.

Which kinds of stem cells are used in medicine?

Two families matter for patients.

Blood-forming (hematopoietic) stem cells. These are the cells in a bone marrow or cord blood transplant. Mayo Clinic describes a bone marrow transplant as a procedure that “infuses healthy blood-forming stem cells into your body to replace bone marrow that’s not producing enough healthy blood cells,” used for leukemias and other cancerous and noncancerous diseases (Mayo Clinic). This is the established, proven form of stem cell therapy, done in hospital transplant programs.

Mesenchymal stromal cells (MSCs). Also called mesenchymal stem cells, these are found in small numbers in bone marrow, fat and umbilical cord tissue. They are the cells regenerative clinics advertise.

Where do the cells come from?

Source	What it is	What to know
Your own bone marrow	Drawn with a needle from the back of the pelvis and spun down into a concentrate in a same-day procedure	One review puts MSCs at about 0.001% of the nucleated cells in bone marrow aspirate (SICOT-J review, 2017), so the concentrate is mostly other cells
Your own fat	Removed by a small liposuction and processed	How it is processed matters legally: a federal appeals court agreed with the FDA in 2024 that one clinic's product, made by breaking fat down with enzymes, was a drug that needed FDA approval (Cooley summary of the ruling)
Donor cord, cord blood, Wharton's jelly, amniotic or placental material, and "exosomes"	Products made from someone else's tissue	Outside the approved uses on the FDA list, these are unapproved. The FDA has warned patients about them, citing reports that include deaths (FDA warning, May 11, 2026)
Cells grown in a lab for days or weeks	Your own or donor cells multiplied in culture	Treated as a drug or biologic. In the United States it belongs in an FDA-authorized clinical trial, not a cash-pay clinic

Sources for the table: <a href="https://www.sicot-j.org/articles/sicotj/fullhtml/2017/01/sicotj160095/sicotj160095.html”>SICOT-J review, 2017; Cooley summary of the ruling; FDA warning, May 11, 2026.

Because so few of the cells in a marrow concentrate are stem cells, any “stem cell count” a clinic quotes deserves a question about how it was measured; a same-day report has limits, set out in what a same-day count can and cannot show.

What has the FDA approved, and what is only being studied?

Status as of September 25, 2026

Approved by the FDA	Being tested in clinical trials	Sold in cash-pay clinics
Cord blood products for blood-forming stem cell transplants (nine listed); OMISIRGE, a processed cord blood product; RYONCIL, donor MSCs for children with steroid-refractory acute graft-versus-host disease (FDA approved products list, updated September 17, 2026)	Uses under study are listed on ClinicalTrials.gov	Bone marrow and fat injections for joints, spine and tendons; donor products; IV infusions. None of these uses is FDA-approved

Sources for the table: FDA approved products list; ClinicalTrials.gov.

A real trial and a paid “study” can look alike; how to tell them apart, and what is being studied outside orthopedics, is set out with trials for neurological and other conditions.

Why do the proven and unproven uses get mixed up?

Four things blur the line, and each is worth recognizing.

One name, two treatments. A bone marrow transplant for leukemia and a marrow injection into a knee are both called stem cell therapy. The first has decades of hospital use behind it; the second has small, short trials. Evidence for one says nothing about the other.

Approved products that are not stem cell treatments. The FDA list also includes cell products such as MACI, a product made from a patient’s own cartilage cells grown in a lab and implanted during knee surgery, and LANTIDRA, donor pancreatic islet cells. Neither is a stem cell injection, so neither is evidence that “stem cells are approved” for your knee.

Listings that look like approval. A trial listing is not approval: the FDA says a ClinicalTrials.gov listing or FDA registration “does not mean the product is legally marketed” (FDA). Paying full price is another tell; the International Society for Stem Cell Research says “it is not customary to pay to be in a clinical trial” (<a href="https://static1.squarespace.com/static/611faaa8fee682525ee16489/t/65f09b1918aebc21ebd37efe/1710267161381/ISSCRPatientHandbookv12Feb2024Redesignv4b.pdf”>ISSCR).

Legal is not the same as proven. Some clinic procedures fall under narrow exceptions that let them be offered without FDA approval. That makes them legal to sell. It does not mean anyone has shown they work, which is the subject of the section on how clinics offer cells without approval, below.

How are the cells supposed to work?

The early idea was that injected cells turn into new cartilage or tendon. The explanation clinics now give is that MSCs release signaling molecules that calm inflammation and support repair. That explanation is based on laboratory and animal research, and it has not been shown to rebuild tissue in human joints.

What happens to injected cells in a human joint is not well mapped, and claims that they travel to damaged tissue come mainly from laboratory and animal work. Tracking studies show how little is settled: in one rat study, the authors wrote that “cell fate and action after transplantation remain unclear,” and the injected cells were found in the knee for about a month but not at two or six months (Scientific Reports, 2019). A clinic that says the cells will “home in” on the damage in your knee is describing a hypothesis, not a finding in people.

What are the risks?

From the harvest. Bone marrow is drawn with a needle from the back of the hip bone. For the diagnostic version of this procedure, Mayo Clinic lists bleeding, infection and lasting discomfort as risks (Mayo Clinic). In UK surveys of diagnostic marrow biopsies, there were 15 adverse events in 20,323 procedures in 2004, most of them bleeding (Bain, Haematologica 2006). A fat harvest is a small liposuction. For cosmetic liposuction, a larger operation, Mayo Clinic lists contour irregularities, fluid buildup, numbness and infection, and rarely internal puncture or fat embolism (Mayo Clinic). How much tissue will be taken, and how, is a fair thing to know in advance.

From the injection. Any needle into a joint can let germs in. Sudden severe pain, swelling, warmth, skin discoloration or fever after an injection can mean a joint infection and need a prompt call (Mayo Clinic). The fuller list, with recovery, is under what to watch for after a procedure.

From unapproved products. The FDA reports “blindness, tumor formation, infections, and more” after unapproved regenerative products (FDA, above), and its 2026 warning cites deaths.

From changing other treatment. Do not stop prescribed aspirin, blood thinners, or treatment for cancer, multiple sclerosis or rheumatoid arthritis to fit an elective injection without the doctor who prescribes it. Mayo Clinic warns that stopping daily aspirin suddenly “may trigger a blood clot and lead to a heart attack” (Mayo Clinic).

Using your own cells avoids rejection by the immune system. It does not make a procedure risk-free.

How can a clinic offer cells without FDA approval?

Federal rules give clinics two narrow ways to use human cells without FDA approval:

• The same surgical procedure exception. A clinic that “removes HCT/P’s from an individual and implants such HCT/P’s into the same individual during the same surgical procedure” (HCT/Ps are human cells or tissues intended to be put into a patient) does not have to follow the FDA’s tissue rules in 21 CFR Part 1271 (eCFR, 21 CFR 1271.15(b)). The rule says the same surgical procedure, not the same treatment plan or the same week, so cells that leave the building or go back in on a different day raise a question.
• Section 361 products. A cell or tissue product avoids premarket approval only if it meets all four conditions in 21 CFR 1271.10(a), including that it is “minimally manipulated” and used for “homologous use only,” meaning it does the same basic job in the body that it did where it came from (eCFR).

Anything outside those paths, including cells grown in a lab and donor products sold for joint injection, is regulated as a drug or biologic and needs FDA authorization to be tested in a trial and approval to be sold. Federal appeals courts have sided with the FDA against clinics that argued otherwise, including the Ninth Circuit in 2024 (Cooley).

Fitting one of these paths is a legal question, not a sign that a treatment works, and only a lawyer can judge whether a specific clinic’s protocol fits. Checking a clinic’s own claims against these rules is the first step in a framework for checking a clinic.

How does it differ from conventional care?

You may hear that conventional care only treats symptoms while stem cells treat the tissue. The evidence does not support that contrast.

	Conventional care for arthritis	Stem cell injections for arthritis
Guideline position (ACR/AF, knee and hip)	Strongly recommends exercise, oral anti-inflammatory medicines and steroid injections, and for the knee, topical anti-inflammatory gels (ACR)	Recommends against (same guideline)
Best evidence on symptoms	Exercise has "a strong body of literature supporting its use for almost all patients with OA" (ACR)	For the knee, a small improvement in pain over placebo, low-certainty evidence (Cochrane review)
Evidence of rebuilding the joint	None claimed	None: no study in the Cochrane review measured arthritis progression on X-ray

Sources for the table: ACR; Cochrane review.

Neither has been shown to rebuild a worn joint. The difference is that conventional first steps have stronger evidence for easing symptoms and guideline support. Cost belongs in the comparison too, starting with getting a written coverage answer from your insurer. The knee page sets out the trials in detail.

Injections also cannot replace surgery for mechanical problems. A torn ACL in someone who needs a stable knee, a meniscus tear that locks the joint, or nerve symptoms from the spine that affect the bladder or legs need a surgeon’s or emergency assessment, not an injection. Telling these apart from problems an injection might address is part of who might consider treatment and when an injection is the wrong tool.

Which page should you read next?

That depends on where you are in the decision. If you are wondering whether an injection makes sense for you at all, start with the candidate page above and then the page for your joint. If you have been offered one of the related treatments sold alongside stem cells, read about platelet-rich plasma and what its trials show or A2M and the state of its evidence. If you are already talking to a clinic, the warning signs of an unproven stem cell clinic are the page to read before you pay.

This page is general information, not medical or legal advice.