Stem Cells, PRP, and Your Knees: A Plain-English Tour of the Research

By Vivonyx · Last reviewed: October 2026

Search “stem cells for knees” and you’ll find two stories: your cartilage can grow back, or it’s all snake oil. The research sits in the middle. Here’s what the stronger trials show, where they fall short, and one thing that often works better than any injection. This isn’t medical advice.

Illustration: Injurymap, CC BY 4.0, via Wikimedia Commons.

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What people mean by "stem cell" for knees

Clinics use several different products under that label:

• PRP — your own blood, spun to concentrate platelets. Not a stem cell product.
• Bone marrow or fat preparations — your own tissue, concentrated at the clinic.
• Umbilical cord / Wharton's jelly MSCs — cells grown from donated cord tissue. (More in Wharton's Jelly vs PRP: What's the Difference?)
• Exosomes — cell-free packets sold on their own.

A study of one doesn't automatically apply to the others. For how MSCs are thought to work, see The Science.

One encouraging trial

In a 26-person randomized trial in Chile, people who got two doses of Wharton's jelly MSCs reported less pain at 12 months than people who got hyaluronic acid. No serious adverse events were reported. MRI scores didn't differ between groups, and several authors worked for the company that made the cells [1]. Small, early trials like this are where the hope comes from. Bigger ones test it.

The reality check

Cochrane review (2025): Across 25 randomized trials (1,341 people), stem cell injections may slightly improve pain and function for up to six months—about 1.2 points on a 0-to-10 pain scale—compared with placebo. The reviewers rated that evidence low certainty [2].

MILES trial (2023): 480 people got bone marrow concentrate, fat-derived cells, cord tissue MSCs, or a steroid shot. At one year, none of the cell options beat the steroid shot or each other, and no group showed a significant MRI change [3].

That doesn't mean "nothing works for anyone." It means large, careful studies haven't yet shown a reliable edge for these injections in knee osteoarthritis. Results vary, and this isn't right for everyone.

What guidelines and regulators say

The American College of Rheumatology and the Arthritis Foundation strongly recommend against both stem cell and PRP injections for knee and hip osteoarthritis, citing inconsistent preparations and techniques [4]. That guideline came out in 2019, before Cochrane and MILES.

The FDA has not approved regenerative medicine therapies for orthopedic conditions such as osteoarthritis or knee pain [5]. Many clinic offerings—including products labeled as Wharton's jelly, stem cells, or exosomes—are not FDA-approved for joint use. If you're researching options, ask about the FDA status of the specific product and whether care is under clinical-trial oversight [5].

The part that is well tested: weight and movement

In the IDEA trial (454 adults with knee osteoarthritis and overweight or obesity), the diet-plus-exercise group lost about 11% of body weight. After 18 months they reported less pain than the exercise-only group [6]. The ACR strongly recommends weight loss and exercise for knee osteoarthritis [4]. Check with your clinician before starting supplements; large trials of glucosamine, chondroitin, and vitamin D have mostly disappointed [4].

Questions worth asking

• What is the FDA status of this product for orthopedic use? Is it under trial oversight (NCT or IND number)? [5]
• What exactly is in the syringe, and which published studies used this product for knees?

There's a similar checklist in MSC Therapy for Neuropathy: What the Research Shows.

FAQ

Do stem cell injections regrow knee cartilage?
Large trials haven't shown that. Some small early trials reported cartilage changes on imaging, but the 480-person MILES trial found no significant MRI change in any group at one year, and the 2025 Cochrane review found no trials measuring structural change on X-ray. Imaging and how a knee feels don't always line up, so both are worth asking about.

Stem cells or PRP: which has better evidence for knees?
Neither has shown a reliable edge in large trials. In the MILES trial, three cell products did no better than a steroid shot or each other at one year. The 2019 American College of Rheumatology and Arthritis Foundation guideline recommended against both stem cell and PRP injections for knee osteoarthritis, though it came out before the newest studies.

Is Wharton's jelly FDA-approved for knees?
No. The FDA has not approved regenerative medicine therapies, including products labeled as Wharton's jelly, stem cells, or exosomes, for orthopedic conditions such as knee osteoarthritis. If you're researching options, it's fair to ask about the FDA status of the specific product and whether it's offered under clinical-trial oversight with an NCT or IND number.

What is the best-studied approach for knee osteoarthritis?
Weight and movement. In the IDEA trial of 454 adults with knee osteoarthritis and overweight, the diet-plus-exercise group lost about 11% of body weight and reported less pain at 18 months than the exercise-only group. The American College of Rheumatology strongly recommends exercise and, where relevant, weight loss. Check with your clinician first.

Not sure where to start?

If you'd like to talk through what you've read, what to ask, or how to get started, email us at hello@vivonyx.com. Or ask the Vivonyx AI assistant any time. You'll get a straight answer, including "the research doesn't know yet" when that's the truth.

Related reading

• Is Stem Cell Therapy FDA Approved?
• Stem Cells for Low Back Pain and Disc Degeneration
• 8 Questions Worth Asking First

Educational disclaimer: This article is for general educational purposes only and is not medical advice, diagnosis, or treatment. It does not describe or suggest the treatment, cure, or prevention of any disease or condition. The cellular and exosome products discussed are generally not FDA-approved for orthopedic use. Talk with a qualified, licensed healthcare professional before making any medical decision.

References

1. Matas J, Orrego M, Amenabar D, et al. Umbilical cord-derived mesenchymal stromal cells (MSCs) for knee osteoarthritis: repeated MSC dosing is superior to a single MSC dose and to hyaluronic acid in a controlled randomized phase I/II trial. Stem Cells Transl Med. 2019;8(3):215-224. https://pubmed.ncbi.nlm.nih.gov/30592390/ (full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC6392367/; NCT02580695)
2. Whittle SL, Johnston RV, McDonald S, et al. Stem cell injections for osteoarthritis of the knee. Cochrane Database Syst Rev. 2025;4:CD013342. https://pubmed.ncbi.nlm.nih.gov/40169165/
3. Mautner K, Gottschalk M, Boden SD, et al. Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial. Nat Med. 2023;29(12):3120-3126. https://pubmed.ncbi.nlm.nih.gov/37919438/ (NCT03818737)
4. Kolasinski SL, Neogi T, Hochberg MC, et al. 2019 American College of Rheumatology/Arthritis Foundation guideline for the management of osteoarthritis of the hand, hip, and knee. Arthritis Care Res. 2020;72(2):149-162. https://pubmed.ncbi.nlm.nih.gov/31908149/
5. U.S. Food and Drug Administration. Important Patient and Consumer Information About Regenerative Medicine Therapies (June 3, 2021). https://www.fda.gov/vaccines-blood-biologics/consumers-biologics/important-patient-and-consumer-information-about-regenerative-medicine-therapies
6. Messier SP, Mihalko SL, Legault C, et al. Effects of intensive diet and exercise on knee joint loads, inflammation, and clinical outcomes among overweight and obese adults with knee osteoarthritis: the IDEA randomized clinical trial. JAMA. 2013;310(12):1263-1273. https://pubmed.ncbi.nlm.nih.gov/24065013/