Who Is a Good Candidate for Stem Cell Therapy?

“Candidate” in this setting is not an FDA-approved indication, and it is not a finding that the treatment is likely to work. It is a clinic’s judgment that your case may be worth considering. The FDA has approved no stem cell product for joint, spine or tendon problems, and the 2019 American College of Rheumatology and Arthritis Foundation guideline strongly recommends against stem cell injections for knee and hip arthritis.

That makes the real question less “do I qualify?” and more “what would an injection be treating in me, and how would I know if it helped?” This page is about that question.

What does “candidate” mean when there is no approved use?

The FDA’s list of approved cell therapies includes cord blood products for blood disorders, one stem cell product for a transplant complication in children, and a few others. None is a stem cell injection for joints, spine, tendons or sports injuries. The one orthopedic cell product on the list, MACI, is made of cultured cartilage cells and is implanted surgically to repair cartilage defects (FDA list of approved cellular and gene therapy products, updated September 17, 2026). Clinics can offer injections outside that list legally only under narrow exceptions, covered under what stem cell therapy is and where it stands with the FDA; none of those exceptions says anything about whether the treatment works.

What does the evidence settle, and what does it leave open?

The most studied use is knee osteoarthritis, and the best summary is a 2025 Cochrane review of placebo-controlled trials. Compared with placebo injections, stem cell injections lowered pain by about 1.2 points on a 0 to 10 scale and improved function by about 14 points on a 0 to 100 scale at three to six months. The reviewers rated that evidence low certainty, because the source, preparation and dose of the cells varied from trial to trial, and they suspected publication bias, since up to three larger trials were withdrawn before reporting results (<a href="https://www.cochrane.org/evidence/CD013342what-are-benefits-and-risks-stem-cell-injections-knee-osteoarthritis”>Cochrane review CD013342). The ACR and Arthritis Foundation recommend against stem cell injections and platelet-rich plasma for knee and hip osteoarthritis (ACR guideline announcement).

That much is settled enough to act on: the average benefit in knee trials is small and uncertain, and the main arthritis guideline advises against the treatment.

Several things are not settled:

• Whether some people do much better than the average. The Cochrane figure is an average across small trials; sample sizes ranged from 6 to 252 people, and only two trials had more than 100 (Cochrane, above). Trials that small cannot tell you reliably which kinds of patients respond.
• Whether any benefit lasts. The main results were measured at three to six months, and no included study measured whether the joint itself changed on X-ray (Cochrane, above).
• Whether the result applies to other joints. Everyone in those trials had knee arthritis. The estimate says little about hips, shoulders, spines or tendons.

What would change the picture is a large placebo-controlled trial of the same kind of product a clinic offers, in people with your joint and stage of arthritis, followed for more than a year. Until then, anyone who tells you with confidence that you will respond is going beyond the evidence, in either direction.

Do the trial patients look like you?

This is the most useful comparison you can make yourself. In the knee trials, the average age of participants ranged from 51 to 66 and symptoms had lasted from one to 10 years (Cochrane, above). If you are much younger, much older, or your problem is not knee arthritis, the trials describe people who are not quite like you, and the numbers should carry less weight in your decision, not more.

It also helps to know which product was tested. Some trials used cells grown in a laboratory for weeks, which cannot legally be offered for knee arthritis outside an FDA-authorized trial. Results from those trials do not describe the same-day bone marrow concentrate a clinic can offer. The difference, and what the knee trials found in detail, is set out on the knee arthritis page.

What does your X-ray grade tell you?

Arthritis on X-ray is often graded with the Kellgren-Lawrence scale (Radiopaedia):

Grade	Definition
0	Definite absence of X-ray changes of osteoarthritis
1	Doubtful joint space narrowing and possible osteophytic lipping
2	Definite osteophytes and possible joint space narrowing
3	Moderate multiple osteophytes, definite narrowing of joint space, some sclerosis and possible deformity of bone ends
4	Large osteophytes, marked narrowing of joint space, severe sclerosis and definite deformity of bone ends

(Osteophytes are bone spurs, and “lipping” means small spurs at the edge of the joint. Sclerosis is hardening of the bone under the cartilage.)

A grade describes what the X-ray shows. It is not, by itself, evidence that an injection will help. If a clinic treats only certain grades, the useful thing to find out is whether that cutoff comes from a controlled comparison or from the clinic’s own experience; the second is an opinion. The same reasoning applies at the hip, shoulder and spine, and for sports injuries, each of which has its own evidence.

Has first-line treatment had a fair chance?

For knee and hip arthritis, the same guideline gives strong recommendations to exercise, which it says has “a strong body of literature supporting its use for almost all patients with OA,” and to self-management programs, tai chi, topical anti-inflammatory gels for the knee, and oral anti-inflammatory drugs and steroid injections for the knee and hip (ACR, above).

What counts as a fair chance is not fixed. In the trials pooled by a 2024 Cochrane review of exercise for knee arthritis, programs lasted anywhere from 2 to 104 weeks (<a href="https://www.cochrane.org/evidence/CD004376exercise-osteoarthritis-knee”>Cochrane review, 2024). So there is no number of sessions after which exercise has officially “failed.” It helps to separate three situations that can all feel like failure:

• The diagnosis was wrong, so the treatment was aimed at the wrong problem. An exercise plan for knee arthritis will not settle pain that comes from somewhere else, and an injection into the same joint would inherit the same mistake.
• The program was never really done. A few unsupervised sessions, or a program stopped when it hurt, is not the same as a structured course with the load increased over time.
• It worked, and the gains faded when it stopped. That points more to keeping the program going than to the joint being unable to respond.

These are reasons to pause before paying for an injection, not universal eligibility rules. If first-line treatment has not been adequately tried, or the diagnosis is still uncertain, it is difficult to know what an injection would be treating, or to tell afterward whether it helped.

When is an injection the wrong tool?

Some problems need urgent care or a different kind of treatment. If one of these fits, a stem cell consultation is not the next step.

Situation	Why an injection does not address it	Where to go
Back pain with new numbness or tingling in the buttocks, backs of the legs or inner thighs, new bladder or bowel problems, or leg weakness	These can signal cauda equina syndrome, which Cleveland Clinic says needs care immediately; delays can cause permanent damage (Cleveland Clinic)	Emergency care today
A torn ACL with a knee that gives way, if you do sports or work that involves pivoting, cutting or heavy manual labor	The American Academy of Orthopaedic Surgeons encourages these patients to consider reconstruction, and warns that ongoing instability risks damage elsewhere in the knee (OrthoInfo)	Orthopedic surgeon
A knee that catches or locks	Catching and locking are common signs of a meniscus tear, and surgery is an option when symptoms persist (OrthoInfo)	Orthopedic evaluation
Advanced arthritis with daily pain despite the proven first steps	Joint replacement is an established option at this stage; the American Academy of Orthopaedic Surgeons calls total knee replacement "one of the most successful procedures in all of medicine" (OrthoInfo). No study in the Cochrane review measured structural change, so there is no trial evidence that an injection restores a worn joint	A joint replacement discussion; see how patients weigh stem cells against joint replacement
A neurological or immune disease	Stem cell use for these conditions belongs in clinical trials	Your specialist, and the conditions being studied in trials

Sources for the table: Cleveland Clinic; OrthoInfo; OrthoInfo; OrthoInfo.

Related pages: how patients weigh stem cells against joint replacement; conditions being studied in trials.

Which health issues should you raise before any procedure?

Some of these are reasons to wait, and some change how a procedure would be done. None of them should be handled by stopping a medicine on your own.

• Aspirin or blood thinners. Bone marrow is drawn with a needle from the back of the pelvis. In UK surveys of diagnostic marrow biopsies, bleeding was the most common complication, and the 2004 survey counted 15 adverse events in 20,323 procedures (Bain, Haematologica 2006). Those were diagnostic biopsies, not harvests for injection, so take the figure as a rough guide. If you take aspirin or a blood thinner for your heart or for clots, do not stop it for an injection without the doctor who prescribed it. Mayo Clinic warns that stopping daily aspirin suddenly “may trigger a blood clot and lead to a heart attack” (Mayo Clinic).
• A current infection, fever, or a skin problem where the needle would go. An injection into or near a joint can carry germs into it (Mayo Clinic on joint infections).
• Medicines for rheumatoid arthritis, multiple sclerosis, cancer or another immune condition. Do not pause, delay or change them to fit an elective injection unless the specialist who prescribes them agrees.

Medicine changes around a procedure belong with the prescriber, and the signs that need a call afterward are listed with the recovery period and warning signs.

What should a clinic be able to explain about your case?

A useful answer to “am I a candidate?” should explain what the clinic thinks is causing your pain, what it would inject, what the trials in people like you found, what else you could do instead, and what the whole plan costs. Some of that can be checked before you visit, using a framework for evaluating a clinic; the rest is for the room, where a list of questions for your first consultation keeps the conversation on those points. Pressure to decide before you have those answers is one of the red flags in stem cell clinics.

The decision that remains

It is not whether you qualify, but whether a small, uncertain average benefit, with its own risks and a price you will likely pay yourself, is worth trying in your situation. What you want from the injection changes that calculation. Someone with advanced knee arthritis who has been advised to have a replacement, but cannot take the recovery time off work this year, may be weighing a stem cell injection against a steroid injection as a way through the next six months. That is a question about short-term symptom relief, which is what the stem cell trials measured, and the guideline recommends the steroid option for the knee. Paying for the same injection in the hope of rebuilding cartilage asks it to do something no included study measured. Either decision is easier to make once the diagnosis is clear and the first-line treatments have had a fair trial, because then you know what the injection would be for and what you would be comparing it against.

This page is general information, not medical advice. Talk with a licensed physician about your own situation.