Stem Cell Therapy for Knees: What the Research Shows

Stem cell therapy for knees is an injection of concentrated cells, most often bone marrow aspirate concentrate (BMAC) or fat-derived stromal vascular fraction (SVF), into an arthritic knee to reduce pain and improve function. Trials show many patients with moderate knee osteoarthritis feel better afterward, but the largest trial to date, by Mautner and colleagues in Nature Medicine (2023), found that no cell injection relieved pain better than a corticosteroid shot at 12 months, and the FDA has not approved any stem cell product for knee osteoarthritis.

At a Glance

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Osteoarthritis affects about 33 million adults in the United States, according to the CDC's osteoarthritis overview, and the knee is one of the joints it strikes most often. For many people with knee osteoarthritis, the options feel limited: physical therapy, anti-inflammatory medications, cortisone injections that wear off faster each time, and eventually the prospect of knee replacement surgery. Stem cell therapy has emerged as a possible middle ground: a biological treatment that aims to calm inflammation and protect cartilage rather than simply masking symptoms.

The sections below cover how stem cell treatment for knees works, how strong the evidence is, who is and is not a good candidate, what the procedure and recovery involve, what it costs, and how it compares with PRP, hyaluronic acid and knee replacement. For the wider picture of the treatment itself, our stem cell therapy treatment guide covers mechanisms and regulation beyond the knee.

How does stem cell therapy for knees work?

Stem cell therapy for knees delivers mesenchymal stem cells (MSCs, also called mesenchymal stromal cells or medicinal signaling cells) into the joint space or the bone just beneath the cartilage. Researchers now think most of the benefit comes from signaling rather than from cells turning into new cartilage. MSCs release growth factors and cytokines that dampen inflammation in the synovium, the lining of the joint, and may slow the breakdown of existing cartilage.

This matters for expectations. A knee injection of BMAC or SVF is best understood as an anti-inflammatory, tissue-supporting treatment for knee pain, not as a cartilage transplant. Clinicians who offer it include orthopedic surgeons, sports medicine physicians, physical medicine and rehabilitation (PM&R) physicians, and interventional pain specialists, usually with ultrasound or fluoroscopic guidance.

Types of Stem Cell Therapy Used for Knees

Not all stem cell treatments are created equal. The cell source matters enormously for both outcomes and regulatory status. These are the three main categories.

Bone Marrow Aspirate Concentrate (BMAC)

BMAC is the most widely used autologous (your own cells) stem cell therapy for knees. A needle is inserted into the iliac crest of the hip bone under local anesthesia, and bone marrow is aspirated. The sample is then centrifuged to concentrate the mesenchymal stem cells, along with growth factors, cytokines, and other regenerative components.

BMAC typically yields 2,000 to 6,000 MSCs per milliliter of concentrate. While this is a relatively small number of stem cells, they are supported by the full biological mix of your bone marrow, including hematopoietic stem cells, platelets, and anti-inflammatory signaling molecules.

Adipose-Derived Stromal Vascular Fraction (SVF)

SVF is obtained through a mini-liposuction procedure, usually from the abdomen or flanks. Fat tissue is a rich source of MSCs, yielding roughly 500 to 1,000 times more stem cells per gram than bone marrow. After harvesting, the fat is processed (enzymatically or mechanically) to isolate the stromal vascular fraction, which contains MSCs, endothelial cells, and pericytes.

The higher cell count is appealing, but SVF processing faces closer FDA scrutiny. Under the FDA's rules for human cells and tissues (21 CFR Part 1271), enzymatic digestion of fat tissue is considered "more than minimal manipulation," which puts many SVF preparations in the category of products that need FDA approval before they can be marketed.

Umbilical Cord and Birth Tissue Products

These products, including Wharton's jelly, amniotic membrane, and cord blood derivatives, are widely marketed as stem cell therapies. Most commercially available products in this category contain few or no viable, living stem cells after processing and sterilization. They do contain growth factors, hyaluronic acid, and extracellular matrix proteins that may have therapeutic value, but calling them "stem cell therapy" is often misleading.

Does stem cell therapy for knees work?

Stem cell therapy for knees reliably improves pain and function compared with where patients started, but it has not clearly beaten simpler injections in head-to-head trials. In the MILES trial, Mautner and colleagues randomized 480 people with Kellgren-Lawrence grade 2 to 4 knee osteoarthritis to BMAC, SVF, umbilical cord tissue MSCs, or a corticosteroid injection. All four groups improved, none of the cell products was superior to the steroid at 12 months, and no group showed a meaningful change on MRI (Mautner et al., Nature Medicine, 2023).

An earlier Mayo Clinic study by Shapiro and colleagues (2017) injected BMAC into one knee and saline into the other in 25 patients with arthritis in both knees. Pain relief was substantial in both knees and did not differ between them (Shapiro et al., American Journal of Sports Medicine, 2017). Placebo effects are strong in knee pain research, which is why trials with a control group carry more weight than before-and-after case series.

The honest summary: stem cell treatment for knees is a reasonable option to discuss for moderate osteoarthritis after conservative care has failed, the evidence for long-term structural benefit is thin, and patients should weigh it against cheaper injections with similar short-term results.

What the Research Shows: Study Results Summary

The evidence for stem cell therapy in knee osteoarthritis has grown substantially over the past decade. The table below summarizes key studies, from small early trials to the largest randomized trial.

Study	Cell Source	Patients	OA Grade	Key Findings	Follow-Up
Shapiro et al. (2017)	BMAC	25	KL 1-3	BMAC in one knee, saline in the other; both knees improved and pain relief did not differ significantly between them; no MRI cartilage change	12 months
Pers et al. (2016)	Adipose MSCs (culture expanded)	18	KL 3-4	Low-dose group showed best pain improvement; well tolerated	6 months
Lamo-Espinosa et al. (2016, 2018)	Bone marrow MSCs (culture expanded) plus hyaluronic acid	30	KL 2-4	Greater WOMAC and pain improvement than hyaluronic acid alone at 12 months, still seen at 4 years	4 years
Freitag et al. (2019)	Adipose MSCs (expanded)	30	KL 2-3	Significant pain reduction and MRI-confirmed cartilage preservation at 12 months	12 months
Hernigou et al. (2020)	BMAC	140	Both knees scheduled for replacement	Subchondral BMAC in one knee, knee replacement in the other; 25 of 140 cell-treated knees (18%) later needed a replacement, at a mean of 10 years	15 years
Kim et al. (2015)	Adipose SVF	18	KL 3-4	Improved WOMAC and VAS scores; arthroscopic evidence of cartilage repair in some patients	24 months
Mautner et al. (2023), MILES trial	BMAC, SVF, umbilical cord MSCs vs. corticosteroid	480	KL 2-4	No cell product was superior to a corticosteroid injection for pain at 12 months; no MRI change in any group; no procedure-related serious adverse events	12 months

The overall pattern: stem cell therapy consistently shows improvements in pain and function for mild-to-moderate knee OA compared with baseline, while controlled comparisons against saline or corticosteroid are less encouraging. Evidence for actual cartilage regeneration is mixed: some studies show cartilage preservation on MRI, but growing new cartilage remains the exception rather than the rule. The longest follow-up comes from Hernigou and colleagues, whose 15-year study in International Orthopaedics suggests that cells placed in the bone beneath the cartilage may delay knee replacement in some patients, though it was an unblinded study from a single group.

Who Is the Best Candidate?

Patient selection is arguably the most important factor in stem cell therapy outcomes. These are the patients who tend to do well, and the ones who do not.

Ideal Candidates

• Kellgren-Lawrence grade 2-3 osteoarthritis: moderate joint space narrowing with some cartilage still present
• Age under 70 (though older patients can still benefit)
• BMI under 35 (excess weight accelerates joint degeneration and may reduce treatment efficacy)
• Failed conservative treatment (physical therapy, NSAIDs, corticosteroid or hyaluronic acid injections)
• Motivated to follow post-procedure rehabilitation protocols
• Want to delay or potentially avoid knee replacement surgery

Not Ideal Candidates

• Kellgren-Lawrence grade 4 (bone-on-bone): there is very little cartilage remaining for stem cells to protect or build upon
• Severe varus or valgus malalignment (knock-kneed or bow-legged deformity): this creates uneven mechanical stress that overwhelms any biological benefit
• Active joint infection or systemic inflammatory conditions that are poorly controlled, such as active rheumatoid arthritis
• Patients expecting full cartilage restoration or a permanent end to knee pain: expectations must be realistic

Your Kellgren-Lawrence grade comes from a standing knee X-ray, and an MRI adds detail about cartilage, meniscus tears and bone marrow lesions. Our osteoarthritis condition page explains how grading works and which treatments match each stage.

The Procedure: What to Expect

A stem cell knee procedure is a same-day outpatient visit with three stages: harvesting cells, processing them, and injecting them into the knee under imaging guidance. Knowing the steps helps reduce anxiety and set expectations.

Before the Procedure

• Stop anti-inflammatory medications (NSAIDs like ibuprofen) at least 1 week before, because they can interfere with the healing response
• Get an up-to-date MRI so your provider can assess cartilage status and plan the injection
• Some providers recommend a "pre-habilitation" program of physical therapy to optimize the joint environment

Day of the Procedure

1. Harvesting (30-60 minutes): For BMAC, bone marrow is aspirated from the posterior iliac crest under local anesthesia and sedation. For SVF, a small liposuction is performed under local anesthesia. Both are outpatient procedures.
2. Processing (20-40 minutes): The harvested material is centrifuged and concentrated in the clinic's lab or a point-of-care processing system.
3. Injection (15-20 minutes): The concentrated stem cell preparation is injected into the knee joint under ultrasound or fluoroscopic guidance to ensure precise placement.

Total time in the clinic: approximately 2 to 3 hours. You will go home the same day.

Recovery and Rehabilitation

• Days 1-3: Mild to moderate soreness and swelling at the injection site and the harvest site (hip or abdomen). Use ice and acetaminophen (not ibuprofen).
• Weeks 1-2: Gentle range of motion and walking are encouraged. Avoid prolonged standing or strenuous activity.
• Weeks 2-6: Gradually increase activity. Low-impact exercise (swimming, cycling, elliptical) is typically cleared by week 3-4. Avoid running, jumping, and heavy lifting.
• Months 2-6: Progressive return to full activity. This is when most patients begin noticing meaningful improvement.

Is stem cell therapy for knees safe?

Autologous BMAC and SVF injections have a low rate of serious complications in published trials. The MILES trial reported no procedure-related serious adverse events across its treatment groups (Mautner et al., 2023). The common side effects are short-lived: knee swelling and a pain flare for a few days, soreness or bruising at the hip or abdominal harvest site, and stiffness.

The larger risks sit with unapproved and poorly manufactured products. The FDA warns that illegally marketed regenerative medicine products have been linked to infections, blindness and tumor formation, and states that these therapies have not been approved for any orthopedic condition, including knee pain and osteoarthritis (FDA patient and consumer information on regenerative medicine therapies). Donor products from birth tissue carry the extra question of how they were processed and tested. Our explainer on which stem cell treatments the FDA has approved covers the regulatory detail.

Cost and Financial Considerations

Stem cell therapy for knees is a significant out-of-pocket expense, and prices vary widely by cell source, region and whether imaging and follow-up visits are bundled. Typical quoted ranges are:

• BMAC procedure: $5,000 to $10,000 per knee
• SVF procedure: $6,000 to $12,000 per knee
• Combined protocols (stem cells + PRP boosters): $8,000 to $15,000 per knee
• Bilateral (both knees): Many providers offer a discount, typically $8,000 to $20,000 total

These costs are almost never covered by insurance, as stem cell therapy for osteoarthritis remains investigational in the eyes of Medicare and most private insurers. Some clinics offer financing plans with monthly payments. Ask for an itemized quote that lists the harvest, processing, imaging guidance and follow-up visits separately.

When evaluating cost, consider the alternative: total knee replacement costs $30,000 to $50,000+ (though largely covered by insurance), requires significant downtime, and carries surgical risks. If stem cell therapy can delay knee replacement by 5 to 10 years, as some long-term data suggests, the out-of-pocket investment may be worthwhile for the right patient. Our breakdown of stem cell knee costs goes further into pricing and what drives it.

Stem cell therapy vs other regenerative therapies for knees

Stem cell therapy is one of several regenerative therapies for knees, and it is the most expensive. Platelet-rich plasma (PRP), hyaluronic acid (viscosupplementation), prolotherapy and corticosteroid injections are the usual comparisons, with total knee replacement as the surgical endpoint. The table compares them on the attributes this post already covers.

Treatment	What is injected or done	Best-studied use in the knee	Evidence summary	Typical coverage
Stem cell therapy (BMAC, SVF)	Concentrated cells from your bone marrow or fat	Moderate osteoarthritis, KL grade 2 to 3	Improves pain versus baseline; not superior to corticosteroid at 12 months in the MILES trial	Cash pay, investigational
Platelet-rich plasma (PRP)	Concentrated platelets from your blood	Mild to moderate osteoarthritis	Several randomized trials favor PRP over hyaluronic acid; results vary by preparation	Usually cash pay
Hyaluronic acid	Lubricating gel (viscosupplement)	Mild to moderate osteoarthritis	Modest benefit; professional guidelines disagree on its value	Often covered
Corticosteroid injection	Anti-inflammatory steroid	Osteoarthritis flares	Fast, short-term relief lasting weeks to months	Covered
Prolotherapy	Irritant solution, usually dextrose	Knee pain and ligament laxity	Small trials; limited evidence	Cash pay
Total knee replacement	Surgical joint resurfacing	Advanced, bone-on-bone osteoarthritis	Established surgical standard for end-stage disease	Covered

For many patients the practical choice is between PRP and stem cells. PRP is less invasive because it needs only a blood draw, and it is priced well below BMAC or SVF. Our guides to platelet-rich plasma treatment and PRP injections for the knee cover that option, and prolotherapy has its own guide. Regenerative medicine for knee pain works best alongside the basics: strength training, weight management and physical therapy remain first-line care for knee osteoarthritis.

Can stem cells help knee injuries like meniscus or cartilage tears?

Stem cell injections for acute knee injuries, such as meniscus tears, ACL injuries and focal cartilage defects, are far less studied than injections for osteoarthritis. Most of the research on regenerative therapies for knee injuries comes from small studies in which cells were added during surgery, so the evidence for an injection alone is thin.

One cell therapy for the knee is FDA approved: MACI (autologous cultured chondrocytes on a porcine collagen membrane), approved in 2016 for symptomatic full-thickness cartilage defects in adults. MACI uses your own cartilage cells, not stem cells, and it requires two surgeries performed by an orthopedic surgeon. If you have a sports injury rather than arthritis, an orthopedic or sports medicine evaluation comes first, because some tears need surgical repair.

How to find a stem cell knee clinic

Start with a clinician who examines the knee, reviews your X-ray and MRI, and tells you your Kellgren-Lawrence grade before quoting a price. Good signs include a physician performing the harvest and injection, imaging guidance for every injection, a clear answer about cell source and processing, and a willingness to say when you are not a candidate.

You can compare providers in the national directory of stem cell therapy clinics, then narrow to your state, for example California stem cell clinics or Florida stem cell clinics. Listing order on Regenerated.com is not paid ranking. Featured slots are labeled and capped. Verified means the clinic completed credential checks, not that it spent more, and the directory is free for patients. Inclusion in the directory is not an endorsement, and our guide to Featured, Verified and organic listings explains each label.

Honest Limitations: What Stem Cells Cannot Do for Your Knee

Responsible providers are transparent about what stem cell therapy can and cannot accomplish:

• It does not grow a new layer of cartilage in most patients. While some studies show cartilage preservation and occasional repair on MRI, the primary benefit is pain reduction and functional improvement, not structural restoration.
• It does not make osteoarthritis go away. OA is a progressive condition. Stem cell therapy may slow the progression and reduce symptoms, but it does not reverse the underlying disease process.
• It has not outperformed simpler injections in the largest trial. In MILES, BMAC, SVF and umbilical cord cells relieved pain about as well as a corticosteroid injection at one year.
• Results are variable. Some patients experience dramatic improvement; others see modest or no benefit. Researchers cannot yet predict with certainty who will respond well.
• It may need to be repeated. Benefits typically last 1 to 5 years, after which a repeat treatment or alternative approach may be needed.

None of this means stem cell therapy is not worth considering. It means going in with realistic expectations is essential for patient satisfaction.

Frequently Asked Questions

How long does stem cell therapy for knees last?

Stem cell therapy for knees typically provides 1 to 5 years of improvement in patients who respond, and some studies report benefit beyond 5 years. Duration depends on the severity of osteoarthritis at the time of treatment, the cell source and count, age, body weight, and how closely you follow rehabilitation. Some patients choose repeat treatments every 2 to 3 years, although no trial has established the ideal interval.

Is stem cell therapy for knees FDA-approved?

No. The FDA has not approved any stem cell therapy for knee osteoarthritis or any other orthopedic condition. Autologous BMAC, made from your own bone marrow, is generally considered compliant with FDA rules when it involves minimal manipulation and homologous use. SVF and birth tissue products face stricter requirements. The treatment is legal when offered within those rules, but it is considered investigational and is paid out of pocket.

Can I walk after stem cell knee injection?

Yes. Most patients walk out of the clinic the same day with mild discomfort, and normal walking is encouraged from day one. The harvest site at the hip or abdomen is often sorer than the knee for the first few days. Plan to take it easy for 2 to 3 days, use ice and acetaminophen rather than ibuprofen, and avoid running, jumping and other impact activities for 4 to 6 weeks.

What is the success rate of stem cell therapy for knees?

There is no single reliable success rate for stem cell therapy for knees, because studies define success differently and many lack a control group. Patients with moderate osteoarthritis (KL grade 2 to 3) tend to do better than those with bone-on-bone grade 4 disease. In the 480 patient MILES trial, every group improved, but no cell product relieved pain better than a corticosteroid injection at 12 months. Be cautious of clinics quoting a precise figure.

Does insurance cover stem cell therapy for knees?

Insurance almost never covers stem cell therapy for knees. Medicare and most private insurers classify BMAC, SVF and birth tissue injections for osteoarthritis as investigational, so patients pay out of pocket, with quoted prices commonly between $5,000 and $15,000 per knee. The office visit, X-ray or MRI that leads to the decision may still be billable to insurance. Ask the clinic for an itemized quote and whether financing is available before booking.

Is PRP or stem cell therapy better for knees?

Neither PRP nor stem cell therapy has shown clear superiority for knee osteoarthritis in head-to-head research. PRP is less invasive, needs only a blood draw, and costs less, so many clinicians try it first for mild to moderate arthritis. Stem cell therapy is usually reserved for patients who want a single biologic treatment and accept a higher price and a harvest procedure. Your osteoarthritis grade and budget usually decide the choice.

Related Reading

This post is part of our full guide to regenerative medicine. For a broader overview of stem cell therapy, including applications beyond the knee, how to evaluate providers, and the latest research, visit our pillar guide: Stem Cell Therapy: The Complete Patient Guide.

Considering alternatives? Read our comparison of PRP vs Stem Cell Therapy: Which Is Right for You? to understand how these two regenerative treatments compare. For nonsurgical options across every stage of joint disease, see our arthritis treatment guide.