Most of what is sold as a stem cell treatment contains very few stem cells.

PRP OR STEM CELLS

PRP contains no stem cells, and most “stem cell” treatments contain very few. In bone marrow concentrate they are under one percent of nucleated cells. Umbilical or amniotic products often hold few or no living cells. Both PRP and cells mainly deliver signal. So PRP comes first for most conditions, and BMAC is the step for more advanced joints.

“Stem cell therapy” is the most oversold phrase in this field. Before comparing it to anything, it is worth pinning down what is actually in the syringe, because the answer is rarely what the marketing implies.

What is the difference between PRP and stem cell injections?

Four quite different things get sold under the same phrase.

• PRP. Concentrated platelets from your blood. It contains no stem cells at all, and nobody serious claims otherwise.
• BMAC. Concentrated bone marrow. It holds a mixed group of cells, and mesenchymal stromal cells are a small fraction — well under one percent of nucleated cells. This is what most American clinics mean by stem cells.
• Adipose-derived preparations. Processed fat tissue. Whether a given prep is legal depends heavily on how much it was altered (manipulated).
• Culture-expanded stem cells. Cells grown in a lab to raise their number. This is what most patients picture. It is not legally available as a routine treatment in the United States outside an approved trial.

Are stem cell injections legal in the United States?

The rules allow same-day procedures using your own tissue (autologous) that is minimally manipulated and used for its normal (homologous) purpose. Draw it, concentrate it, put it back in one visit, and you are inside that line. Grow cells over days or weeks to multiply them, and you have created a drug. A drug needs approval, and these products do not have it.

This matters to you in practice. Some clinics offer “expanded” cells here, or arrange treatment abroad to get around the rule. They are working outside a framework that exists because unregulated cell products have caused real harm. That harm includes blindness, from injections into the eye at an unapproved clinic. The rule is not red tape.

Do umbilical cord and amniotic injections contain living stem cells?

Be extra careful here. Some products are sold as umbilical cord or amniotic stem cell injections. They are widely marketed, often at seminars aimed at older patients. Independent analyses have repeatedly found that samples on the market contain few or no living cells by the time they are injected. Freezing (cryopreservation) and processing kill them.

These are allogeneic — from a donor. That removes the main safety argument for using your own tissue. And they are often the most expensive option on the menu. If a clinic offers you a product from someone else’s tissue as a stem cell treatment, ask for the viability data (data showing the cells are alive). There usually is not any.

What the cells are probably doing anyway

Say living mesenchymal cells truly are delivered. Even then, they most likely do not work the way the name suggests. They do not appear to settle in (engraft) and become new cartilage in any meaningful amount. The current understanding is paracrine. The cells release signaling molecules and extracellular vesicles that modulate inflammation and influence the cells already there. Then they largely disappear within days.

If that is the mechanism, the gap between a cell prep and a growth-factor prep like PRP narrows a great deal — both end up delivering signal. That fits the head-to-head trials. Most of them fail to find the large advantage the pricing implies.

Is stem cell therapy better than PRP?

Cell-based treatments usually cost several times what PRP costs. We do not publish prices here, but the ratio is the point. The price gap is much larger than the evidence gap. In knee osteoarthritis, direct comparisons between BMAC and PRP have generally found no significant outcome difference at a year.

Paying substantially more for an equal result, through a more invasive procedure, is a poor trade in an earlier-stage joint. Where the joint is further along, the math changes. The reasons are set out on bone marrow aspirate concentrate. It is not a poor trade in every case, and that is what the next section is about.

When does a cell-based treatment make sense?

• Osteonecrosis (bone death), especially of the femoral head, where marrow-based treatment has the strongest case of any use discussed here
• More advanced joint degeneration where PRP has been tried and gave a partial answer
• Involvement of the bone under the cartilage (subchondral bone), where the problem sits in bone, not only in cartilage
• As a planned step up, on evidence, not as a first move

How to read a clinic that offers this

• Does it name the specific product, or only say “stem cells”?
• Can it tell you the cell content of what you are receiving, or is it assumed?
• Does it claim to regrow cartilage? Nothing available today reliably does.
• Does it use before-and-after imaging as proof? Change on X-ray is not what these treatments produce.
• Is it a same-day procedure using your own tissue, or something shipped in frozen?
• Does it recommend PRP first for the indications where PRP performs well — or is everyone steered to the most expensive option?

What we do here

PRP first for most uses, because it performs well, costs less and carries the lower risk. BMAC where the tissue is further gone or the specific problem argues for it. No donor (allogeneic) products, no expanded cells, and no use of the phrase “stem cell therapy” for something that is mostly platelets and signaling molecules.

The reason for caution is not caution for its own sake. This corner of medicine has an unusually high ratio of confident marketing to published evidence. And the people most exposed to it have already been failed by several other treatments and are running out of options.

Why the marketing is so much louder than the evidence

The money explains most of it. These are cash-pay treatments, so the money comes straight from patients, not from an insurer with a review process. That removes the usual brake. No prior authorization asks whether the use fits. No medical director compares your case to a policy. And no claims data piles up somewhere for anyone to review.

It also draws a certain audience. The people most willing to pay out of pocket for a regenerative treatment are, by definition, the people for whom covered treatments have already failed. That is a group in some distress, with less bargaining power. A seminar aimed at that group, promising cartilage regrowth, is not selling into a doubting market.

None of this means the science underneath is empty. It means how loud a claim is has nothing to do with how well it is supported. The burden should sit on the clinic to show you what it is delivering, not on you to disprove it.

What would change our position

Since this page is critical, it seems fair to say this openly. Here is what would change our view. Adequately powered randomized trials would need to show a consistent, clinically meaningful advantage for a cell-based prep over PRP in a named use. Then we will revise it. The prep must also be described well enough to reproduce. For osteonecrosis, that case is already reasonable. For knee osteoarthritis and for tendinopathy it is not there yet, and we will say so until it is.

What people ask about stem cell offers

Is PRP a stem cell treatment?

No, and any clinic saying so is describing it wrongly. PRP contains platelets, not stem cells. How PRP works.

Can I get real expanded stem cells somewhere?

Not routinely in the United States outside an approved trial. Treatment abroad carries real risk. What BMAC actually is.

Are umbilical cord injections worth it?

Independent testing has repeatedly found few or no living cells in samples on the market. Risks and side effects.

Will any of this regrow my cartilage?

No available treatment reliably does. Anyone claiming otherwise is overselling. PRP for knee osteoarthritis.

Does bone marrow concentrate (BMAC) contain stem cells?

Some, but far fewer than the name suggests. BMAC is a mixed group of cells, and mesenchymal stromal cells make up well under one percent of the nucleated cells. It is drawn, concentrated and returned in one visit, with nothing grown in a lab. It is what most American clinics mean by stem cells. We do not call it stem cell therapy, because that oversells what is in the syringe.

Do stem cells turn into new cartilage?

Not in any meaningful amount. Even when living mesenchymal cells are delivered, they do not appear to settle in and become new cartilage. The current understanding is that they release signaling molecules that calm inflammation and influence the cells already there. Then they mostly disappear within days. That puts them much closer to PRP than the marketing suggests, since both mainly deliver signal.

Should I try PRP or stem cells first?

For most conditions, PRP comes first. It performs well, costs less and carries the lower risk. We move to BMAC when the tissue is further gone, or when PRP gave only a partial answer. We also move to it when the specific problem calls for marrow, such as osteonecrosis of the femoral head or disease in the bone beneath the cartilage. We use no donor products and no lab-expanded cells.

What should I ask a clinic offering stem cell injections?

Ask which specific product it uses and what the cell content is. Ask whether it is your own tissue, drawn and returned the same day, or something shipped in frozen. Be wary of any promise to regrow cartilage, and of before-and-after images offered as proof. Last, ask whether it recommends PRP first where PRP works well, or steers everyone to the most expensive option.

What is the downside of stem cell therapy?

The genuine version, your own bone marrow, costs you a second procedure. The marrow is drawn from the top of the hip bone, that site can ache for several days and sometimes more than the treated joint, and because an infection there would start at bone, the harvest carries preventive antibiotics that PRP does not need. The yield is also out of your hands on the day: age, smoking and insulin resistance all thin the marrow, so two people can sit through the same harvest and receive very different biology. What a marrow harvest involves. How its infection risk differs from a PRP injection’s.

Related reading

• Bone marrow aspirate concentrate
• PRP compared with BMAC
• How PRP works
• Am I a candidate?