Stem Cell Therapy vs PRP Injections for Knee Arthritis: Which Is Better?
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By Dr. Jeffrey Peng, MD · Published March 6, 2026 · 6 min read
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Platelet rich plasma injections and stem cell injections are two of the most talked-about orthobiologic treatments for knee osteoarthritis. Both have demonstrated clinically significant pain relief and functional improvement in clinical trials. However, stem cell therapy is often marketed as a superior treatment and comes with a much higher price tag. But does the evidence actually support that claim? A landmark randomized controlled trial directly compared adipose derived stem cell injections to PRP for knee arthritis — and the results may surprise you.
As a sports medicine physician who specializes in orthobiologic treatments, I review the latest evidence on stem cells versus PRP so you can make an informed decision about your treatment options.
Why Are We Moving Away from Cortisone Injections for Knee Arthritis?
Nonoperative treatment options for knee arthritis include exercise therapy, oral anti-inflammatory and pain medications, topical medications, and injection therapy. For decades, cortisone injections were the standard of care. However, we are rapidly moving away from steroid injections because multiple studies have demonstrated that cortisone damages cartilage and accelerates the progression of arthritis over time.
This is precisely why orthobiologic treatments — including PRP injections and stem cell therapy — have gained so much attention. These treatments aim to harness the body's own healing mechanisms to reduce inflammation, relieve pain, and potentially slow the degenerative process rather than accelerate it.
How Does PRP Compare to Other Knee Arthritis Treatments?
I have covered PRP injections extensively for the treatment of symptomatic knee arthritis. The evidence base for PRP is remarkably strong. Multiple randomized controlled trials have compared PRP to placebo, PRP to cortisone, and PRP to hyaluronic acid — and PRP consistently outperforms each of these alternatives. Patients treated with PRP report significant and sustained improvements in pain, function, and quality of life.
The data supporting PRP for knee arthritis is by far the most robust of any orthobiologic treatment currently available. This is an important point to keep in mind as we explore how stem cells compare.
Are Adipose Stem Cell Injections Better Than PRP?
In theory, stem cells should provide even greater symptom relief than PRP. That is how many healthcare providers market them, and it is also why stem cell procedures cost significantly more. Adipose derived stem cells have become a particularly promising option because the harvesting process yields an extremely high number of mesenchymal stem cells and pericytes, especially compared to other sources such as bone marrow.
While previous clinical trials have shown that adipose derived mesenchymal stem cells provide meaningful symptom relief for knee arthritis, no randomized controlled trial had ever directly compared adipose stem cells to PRP — until this study.
What Did This Randomized Controlled Trial Find?
This prospective randomized controlled trial enrolled 118 patients with symptomatic knee osteoarthritis and randomized them to receive either a single injection of microfragmented adipose tissue or a single injection of PRP. Patients were evaluated by blinded clinicians at 1, 3, 6, 12, and 24 months using validated pain and functional outcome scores. MRI imaging was also performed at 6, 12, and 24 months to assess arthritis progression.
The results were striking:
The adipose stem cell group showed statistically significant improvements in nearly all clinical scores. Interestingly, improvements were similar across all severity levels of arthritis, meaning patients with both mild and severe disease benefited. However, younger patients achieved greater improvements compared to older patients.
The PRP group also demonstrated statistically significant improvements in nearly all clinical scores. Consistent with existing literature and systematic reviews, patients with mild osteoarthritis experienced greater improvements than those with more severe disease. Similar to the stem cell group, younger patients also fared better than older patients.
When the researchers performed comparative analysis between the two groups, they found no statistically significant differences in pain or functional outcomes between adipose stem cell therapy and PRP at any time point throughout the 24-month study period.
Do Stem Cells Work Better for Severe Arthritis?
Subgroup analyses revealed that patients with mild osteoarthritis had better outcomes overall, but there were no differences between the adipose stem cell and PRP groups. The only notable finding was among patients with moderate to severe arthritis: those treated with adipose stem cells showed better improvement in one functional score at 6 months compared to PRP. However, by 12 and 24 months, these differences disappeared entirely.
Imaging outcomes were equally reassuring. Both X-ray and MRI studies showed no deterioration in arthritis severity at 6, 12, and 24 months for either treatment group. There were no statistically significant differences between groups on imaging.
The study authors concluded that both adipose stem cells and PRP provided significant and similar clinical improvement up to 24 months of follow-up in patients with symptomatic knee osteoarthritis (Zaffagnini et al., 2022).
Why PRP Remains the Best Orthobiologic Treatment for Knee Arthritis
Many healthcare providers counsel patients that stem cells are far superior to PRP and produce significantly better outcomes. This study suggests otherwise. In fact, in a separate randomized controlled trial comparing PRP to bone marrow stem cell injections, the results were remarkably similar — PRP produced equivalent benefits to stem cells.
Not only does PRP produce comparable outcomes, it is also significantly cheaper and far easier to obtain. PRP requires only a routine blood draw. There is no fat harvesting, no bone marrow aspiration, and no surgical procedures involved. The simplicity and accessibility of PRP make it the most practical orthobiologic option for most patients.
There may be one potential advantage for stem cell therapy: patients with severe arthritis. This study suggests that adipose stem cells may offer a modest short-term benefit for those with advanced disease. However, the advantage was only observed at 6 months and was no longer present at 12 and 24 months.
In my practice, PRP remains my first-line orthobiologic treatment for symptomatic knee arthritis regardless of age or severity. The data supporting its use is the most robust of any orthobiologic, and it is also the most cost-effective. For patients with more severe arthritis, I still recommend trying PRP first. You may need more frequent booster injections, but the chances of meaningful symptom relief remain high. If PRP eventually becomes less effective and you are still looking to avoid a knee replacement, that may be the appropriate time to consider stem cell therapy.
If you would like to learn more about whether PRP or other orthobiologic treatments may be right for you, I encourage you to schedule a consultation to discuss your options.
References
1. Zaffagnini S, Andriolo L, Boffa A, et al. Microfragmented Adipose Tissue Versus Platelet-Rich Plasma for the Treatment of Knee Osteoarthritis: A Prospective Randomized Controlled Trial at 2-Year Follow-up. Am J Sports Med. 2022;50(11):2881-2892. doi:10.1177/03635465221115821
Medical Disclaimer: This content is for educational purposes only and does not substitute for the medical advice of a physician. Always consult your healthcare provider before beginning any new treatment program. The information presented reflects the opinion of Dr. Jeffrey Peng and does not represent the views of his employers or affiliated hospital systems.
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