The best available clinical evidence does not show that stem cell injections reliably outperform standard treatments for knee osteoarthritis. The largest randomized trial to date, the MILES study, found that stem cell injections were not statistically superior to corticosteroid injections at 12 months. That does not mean stem cells did nothing. Patients in every study arm improved from baseline, and a Cochrane evidence review describes the benefit as modest, with quality of evidence still uncertain.
For some patients, particularly those who want to avoid repeated steroid exposure or who have not responded well to it, stem cell therapy remains a reasonable option to discuss. It is not a proven substitute for surgery in advanced cases, and no trial has shown it regrows cartilage at a meaningful scale.
If you have knee osteoarthritis and are weighing this option, here is what matters before you book a procedure: For more details on managing arthritis symptoms and treatment options, see this pain relief and mobility guide.
- Ask what the evidence actually supports, not what a clinic website claims
- Understand which stem cell source (bone marrow, fat, or umbilical cord tissue) a provider plans to use
- Get a candidacy evaluation from an orthopedic or regenerative specialist before paying out of pocket
Key Takeaways
Stem cell injections for knee osteoarthritis show similar 12 month outcomes to corticosteroid injections in the largest randomized trial conducted, with modest but uncertain benefit confirmed by systematic review.
| Point | Details |
|---|---|
| MILES trial result | Three MSC types showed no statistically significant advantage over corticosteroid at 12 months in 480 patients. |
| Cochrane conclusion | Evidence suggests modest pain and function improvement, but certainty of evidence remains low to moderate. |
| Cost reality | Out-of-pocket costs commonly run several thousand dollars per knee, largely uncovered by insurance. |
| Candidate profile | Mild to moderate osteoarthritis with partial response to conservative care fits best; severe bone-on-bone cases usually need surgical evaluation. |
| Where to start | Nowak Orthopedic Associates evaluates candidacy for PRP, orthobiologic injections, and surgical options before recommending a path. |
This article is general information, not a substitute for advice from a qualified doctor. Consult a qualified healthcare professional about your own circumstances before acting on anything here.
Table of Contents
- What the Research Says About Stem Cell Knee Arthritis Treatment
- How Stem Cells Work and What Products Clinics Actually Use
- How It Compares to Corticosteroids, PRP, and Hyaluronic Acid
- Safety, Regulation, and What Treatment Actually Costs
- What Happens During the Procedure and Recovery
- Questions to Ask Before You Book Stem Cell Therapy
- A Note From Dr. Roger Nowak and Nowak Orthopedic Associates
- Editorial Perspective on Stem Cell Therapy for Arthritis
- Get an Honest Evaluation Before You Choose a Treatment Path
- Sources
- FAQ
What the Research Says About Stem Cell Knee Arthritis Treatment
The strongest data point we have comes from the MILES trial, a randomized phase 3 study that enrolled 480 participants across multiple U.S. sites. Researchers split patients into four groups: three received different types of mesenchymal stem cells (bone marrow, adipose tissue, or umbilical cord derived), and the fourth received a standard corticosteroid injection. At 12 months, no group showed statistically significant superiority over the others in pain or function scores. Every group improved, including the corticosteroid group.
The core finding: three types of stem cell injections performed no better than a corticosteroid shot at one year, in the largest trial ever run on this question.
That is a meaningful result, and it cuts against a lot of marketing language you may have seen. It does not mean stem cells are worthless. It means that, head to head, they have not yet proven themselves to be the better choice for the average knee osteoarthritis patient.
The Cochrane systematic review adds useful context. It concludes that stem cell injections may offer a slight improvement in pain and function compared with placebo, but it labels the certainty of that evidence as low to moderate. Cochrane’s caution stems from a real problem in this field: study heterogeneity.
- Cell sources vary widely (bone marrow, fat, umbilical cord tissue), and each behaves differently
- Dosing is not standardized across clinics or trials
- Patient selection criteria differ, making it hard to compare outcomes fairly
- Most trials follow patients for only 12 months, leaving long-term durability unanswered
Academic centers echo this caution. Commentary from Duke Health on the MILES results urges patients to be skeptical of clinics promising cures or guaranteed surgery avoidance. Longer-term follow-up data from MILES and related trials, tracking patients past two or three years, would need to show a durability advantage over corticosteroids to change how we counsel patients. Right now, that data does not exist.
How Stem Cells Work and What Products Clinics Actually Use
Stem cell injections do not appear to regrow significant amounts of new cartilage in the way early marketing suggested. What they seem to do, based on current understanding, is release anti-inflammatory and trophic (supportive) signals inside the joint. Think of it less like planting new tissue and more like sending in a repair crew that calms inflammation and encourages the joint’s own cells to function better. The Arthritis Foundation describes this as an evolving area of regenerative medicine, not a settled cure.
Three product types dominate clinical use for knee osteoarthritis:
- Bone marrow aspirate concentrate (BMAC): cells drawn from your pelvic bone, concentrated in a centrifuge, then injected the same day
- Adipose-derived stromal vascular fraction (SVF): cells harvested through a mini-liposuction procedure, typically from the abdomen or thigh
- Umbilical cord–derived MSCs: an allogeneic (donor-sourced) product, often cryopreserved and shipped ready to use
All three were tested head-to-head in the MILES trial. BMAC and adipose SVF require an extraction step from your own body, adding procedural time and a second injection site. Umbilical cord MSC skips that step since it is not harvested from the patient, which raises separate questions about sourcing and regulatory oversight. Injections are typically delivered under ultrasound guidance to place the cells accurately inside the joint capsule.
Pro Tip: Ask your provider directly which of the three cell sources they use and why. If they cannot explain the tradeoffs between BMAC, adipose SVF, and umbilical cord MSC, that is a sign to get a second opinion.
How It Compares to Corticosteroids, PRP, and Hyaluronic Acid
Corticosteroid injections still work faster for short-term flare relief, often within days. The MILES data shows that by 12 months, stem cell groups land in roughly the same place as corticosteroid patients, just by a slower and more expensive route. If speed and cost matter more to you than avoiding steroids, corticosteroids remain a hard option to beat for a single flare.
Platelet-rich plasma (PRP) and hyaluronic acid, sometimes called viscosupplementation, sit in a different evidence category. PRP has a growing but still mixed evidence base for pain relief in mild to moderate osteoarthritis. Hyaluronic acid works by supplementing the joint’s own synovial fluid, the natural lubricant that cushions the knee, and tends to suit patients with milder cartilage wear who want to delay more invasive options.
- Corticosteroid: fastest onset, lowest cost, best for acute flares
- PRP: moderate evidence, appeals to patients wanting an autologous option without stem cell harvesting
- Hyaluronic acid: supports joint lubrication, generally best for early to moderate osteoarthritis
- Stem cell injections: similar 12-month outcomes to corticosteroid in trial data, higher cost, no proven long-term edge
When cartilage loss is advanced and bone-on-bone contact limits daily function, injections of any kind lose relevance, and surgical evaluation for procedures like unicompartmental or total knee arthroplasty becomes the appropriate conversation. Paying a premium for stem cells only makes sense if your goals and joint condition justify it, since the trial evidence has not shown a durability advantage that offsets the added cost.
Safety, Regulation, and What Treatment Actually Costs
Both MILES and the broader research base report low rates of serious adverse events from stem cell knee injections. Most reported side effects are mild and procedural: injection-site soreness, temporary swelling, or a brief flare in joint pain that resolves within days. No trial has flagged a signal for major safety concerns tied to the cell types studied.
The regulatory picture is more nuanced than most clinic marketing lets on. Autologous products, meaning cells taken from and returned to the same patient in one procedure, generally face a different oversight pathway than allogeneic products like donor-sourced umbilical cord MSC, which involve additional processing and distribution steps. A PMC review of stem cell therapies for osteoarthritis walks through these distinctions in more depth.
Cost is where patients get caught off guard. Clinic pricing guides commonly cite out-of-pocket costs in the range of several thousand dollars per knee, and most insurance plans do not cover the procedure since it is still considered investigational for osteoarthritis. Before paying, confirm these basics:
- Ask whether the clinic uses sterile, accredited processing for cell preparation
- Ask for the actual cell count or dose being injected, not just the product name
- Confirm the injection will be done under ultrasound or imaging guidance
- Review the informed consent document for any language overstating outcomes
- Ask whether the clinic tracks and shares its own patient outcome data
What Happens During the Procedure and Recovery
A stem cell injection visit starts with a thorough evaluation: a physical exam, review of prior imaging to confirm the severity of osteoarthritis, and a check on what conservative treatments (physical therapy, weight management, bracing) you have already tried. This step matters because candidacy depends heavily on how much cartilage damage is present.
- If using an autologous product, your provider draws bone marrow or fat tissue in a short outpatient procedure, then processes it in a centrifuge
- The concentrated cells (or the ready-to-use umbilical cord product) are injected into the knee under ultrasound guidance
- The entire visit typically takes under two hours, including preparation and processing time
- You go home the same day with basic activity restrictions
Most patients notice initial changes between four and 12 weeks, with some continued improvement reported up to 12 months. Mild swelling or soreness for a few days is expected. Contact your provider promptly if you notice worsening pain, fever, redness, or drainage at the injection site, since those can signal infection.
Questions to Ask Before You Book Stem Cell Therapy
Not every knee osteoarthritis patient is a good candidate. Generally, people with mild to moderate cartilage loss who have tried and only partially responded to conservative care fit the profile best. Patients with severe bone-on-bone arthritis, significant joint deformity, or unrealistic expectations about “regrowing” cartilage are less likely to benefit.
Before scheduling treatment, ask your provider:
- What is my osteoarthritis grade, and does it fit the profile of patients who respond to injections?
- Which cell source will you use, and what is the actual dose?
- Do you track and share outcomes from your own patients?
- What happens if I see no improvement? Is there a follow-up plan or refund policy?
Walk away from any provider promising a guaranteed cure or telling you this will let you avoid surgery altogether. Reasonable providers combine orthobiologic injections with physical therapy, weight management, and bracing rather than positioning the injection as a standalone fix.
Pro Tip: Bring a written list of every treatment you have already tried, including dates and how long relief lasted. It gives your provider the clearest picture of whether you are a strong candidate.
A Note From Dr. Roger Nowak and Nowak Orthopedic Associates
Dr. Roger B. Nowak is a board-certified orthopedic surgeon with a practice focus on minimally invasive procedures for the shoulder, knee, elbow, and hand. Through the Regenerative Clinic at Nowak Orthopedic Associates, patients receive an individualized evaluation covering imaging review, prior treatment history, and osteoarthritis grade before any orthobiologic option, including PRP, stem cell injections, or SoftWave therapy, is recommended. The goal is matching each patient to the option the evidence actually supports, not the one that sounds most impressive.
Editorial Perspective on Stem Cell Therapy for Arthritis
The MILES results deserve more attention than most clinic marketing gives them, because “no statistical difference from corticosteroid” is not the same story a lot of patients have been sold. Somewhere along the way, stem cell therapy got framed as a near-miraculous alternative to surgery. The data does not back that framing, and I think patients deserve the unvarnished version.
Here is where I push back on conventional advice: too many resources treat “not proven superior” as equivalent to “not worth considering.” That is an overcorrection. A treatment that matches corticosteroid outcomes without repeated steroid exposure still has a place for the right patient, particularly someone managing frequent flares who wants to avoid the joint tissue effects of long-term steroid use.
What I would prioritize first is not the injection type. It is an honest conversation about your osteoarthritis grade, what you have already tried, and what “success” actually means to you. Cost and hype should come last in that conversation, not first.
— Dr. Roger Nowak
Get an Honest Evaluation Before You Choose a Treatment Path
Given how much clinic marketing overstates what stem cell injections can do, the clearest advantage Nowak Orthopedic Associates offers is a candidacy evaluation grounded in your actual imaging and osteoarthritis grade, not a sales pitch for the most expensive option on the menu. The Regenerative Clinic reviews PRP, orthobiologic injections, and SoftWave therapy alongside surgical options, so you get a plan built around your knee, not a single product line. If surgery ends up being the right call instead, that conversation happens under the same roof rather than sending you elsewhere. Ready to find out where you stand? Schedule your first visit and bring your imaging and treatment history so Dr. Nowak can give you a direct answer on candidacy.
Sources
- Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial
- What are the benefits and risks of stem cell injections for knee osteoarthritis?
- Regenerative Medicine: Helping the Body Heal Itself
- Multicenter Trial of Stem Cell Therapy for Osteoarthritis (MILES) — NCT03818737
FAQ
How effective is stem cell therapy for knee arthritis?
The MILES trial found stem cell injections improved pain and function from baseline but were not statistically superior to corticosteroid injections at 12 months, and Cochrane rates the overall evidence as modest with limited certainty.
What is the best treatment for arthritis in the knees?
There is no single best treatment. It depends on osteoarthritis severity, with corticosteroids, PRP, or hyaluronic acid suited to mild to moderate cases and surgical evaluation appropriate for advanced bone-on-bone arthritis.
How much does a stem cell injection cost for a knee?
Clinic pricing guides commonly cite several thousand dollars per knee out of pocket, since most insurance plans do not cover stem cell injections for osteoarthritis.
How long does a stem cell injection for knees last?
Trial data tracks outcomes reliably out to 12 months, with some patients reporting continued improvement through that period, but longer-term durability beyond a year has not been firmly established.