By Vivonyx · Last reviewed: November 2026
A torn meniscus is one of the most common knee injuries [1], and you may have seen "stem cells" mentioned as an option in a headline or a forum. So here's the question this article tries to answer: what does the human research actually show about stem cells for meniscus tears?
It's education, not medical advice.
Meniscus tears in one minute
The menisci are two rubbery, C-shaped disks that cushion the knee. They can tear from a sudden twist, or slowly as the tissue wears with age [1]. Common symptoms include pain, swelling, stiffness, and a catching or locking feeling [1].
Blood supply is the key detail. The outer third of the meniscus has a good blood supply and can sometimes heal or be repaired. The inner two-thirds has very little, and tears there generally can't heal on their own [1]. Many tears don't need immediate surgery, while others are trimmed (partial meniscectomy) or stitched (repair) [1].
Losing meniscus tissue is linked with a higher risk of knee arthritis later [2][3]. That's the gap researchers hope cells might help with.
What researchers have tried
Human studies have tested cells in three main ways:
An injection after the meniscus is trimmed, to see whether tissue grows back.
Cells added during surgical repair, to see whether the stitched tear heals better.
Cells loaded onto a meniscus "scaffold", an implant that fills in missing tissue.
The cells also differ: donor cells, a person's own cells from bone marrow, blood, or the knee's lining (synovium), and lab-grown cells made from embryonic stem cells. Our Wharton's jelly vs. bone marrow article explains why the cell source matters.
The main human studies of stem cells for meniscus tears. Educational summary of the sources cited in this article.
What the human studies found
The short version: one randomized trial, plus very small studies without a comparison group.
The randomized trial (55 people, U.S.). After a partial meniscectomy, people got a knee injection of donor MSCs at one of two doses, or a hyaluronic acid control. At 12 months, meniscus volume grew by at least 15% on MRI in 24% of the lower-dose group and 6% of the higher-dose group, versus none of the controls. So most people who got cells didn't reach that mark. People with arthritis changes who got cells reported less pain than controls [4].
Cells during repair (5 people, U.K.). For tears in the low-blood-supply zone, surgeons placed a person's own bone marrow MSCs on a collagen scaffold inside the tear before stitching. At 2 years, 3 people had no symptoms and no sign of a new tear on MRI; 2 needed the torn part removed at about 15 months [2].
Cells from the knee lining (Japan). In two small reports of 5 and 6 people with degenerative tears, cells were added two weeks after repair. Knee scores improved. In the second report, a look inside the knee at one year showed the damaged area fully or partly restored in all 4 people with flap tears, and both radial tears had healed [5][6]. Neither had a control group.
Scaffold with or without cells (17 people, Mexico). Adding MSCs to a meniscus implant showed no advantage over the implant alone for nearby cartilage at 12 months [3].
Lab-made cells (18 people, China). A phase I safety trial of cells derived from human embryonic stem cells reported that the injections were safe over 12 months. Phase I trials mainly test safety and dose, not whether something works [7].
Our knee arthritis research tour covers the larger knee arthritis trials.
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What reviews and expert groups say
A 2017 systematic review found only 4 human studies to analyze and concluded there isn't enough evidence that stem cells form lasting new meniscus tissue in people [8].
Two 2021 reviews found insufficient high-quality evidence for "meniscal volume restoration" [9], and said the best cell source and delivery method can't be determined yet without larger, longer randomized trials [10].
A 2026 expert review said MSCs and other "biologic augmentation" options for meniscus repair rest on limited, low-quality clinical evidence, and that routine use "warrants critical evaluation" [11].
A 2026 international expert consensus on orthobiologics couldn't agree on some statements about cell therapies made from a person's own tissue, and named dosing, preparation, and quality control as unresolved [12].
Safety
The randomized trial found no clinically important safety issues [4]. One small report noted knee swelling, warmth, and a raised inflammation marker, which may have come from the surgery itself [5]. But these studies were small and short. The FDA has received reports of blindness, tumor formation, and infections linked to unapproved regenerative medicine products [13]. Our 8 questions article covers what's worth asking about any product.
FDA status and clinical trials
The FDA says the only FDA-approved stem cell products are blood-forming stem cells from umbilical cord blood, approved for certain disorders of blood production [14]. It also says regenerative medicine products have not been approved for any orthopedic condition, including knee pain [13]. Our guide Is Stem Cell Therapy FDA Approved? explains what approval means.
A ClinicalTrials.gov search for meniscus and mesenchymal cells returns 5 listings: 3 completed and 2 with an unknown status. None has posted results on the site [15]. The FDA cautions that a ClinicalTrials.gov listing doesn't, by itself, mean a product is legally marketed [13].
What we still don't know
Whether cells help tears heal better than standard care. Only one randomized trial exists, and it measured regrowth after trimming, not tear healing [4][8].
Which cells, dose, and method work best, if any [10][12].
Whether any effect lasts. Follow-up has mostly been 2 years or less [8][10].
Frequently asked questions
Can stem cells regrow a torn meniscus? Not reliably, based on current human studies. In one randomized trial, a minority of people who got cell injections after meniscus trimming showed measurable regrowth on MRI, and reviews say there isn't enough evidence of lasting new tissue [4][8].
Have stem cells for meniscus tears been tested in randomized trials? One randomized trial of 55 people has been published. Most other human studies included 5 to 18 people and had no comparison group [4][2][7].
Are stem cells used during meniscus repair surgery? Only in small research studies so far. Expert reviews call the evidence limited and low quality [11].
What kinds of cells have been studied for meniscus tears? Donor MSCs, a person's own MSCs from bone marrow or the knee lining, and lab-made cells derived from embryonic stem cells [4][2][5][7].
Is stem cell therapy FDA-approved for meniscus tears? No. The FDA says regenerative medicine products have not been approved for any orthopedic condition, including knee pain [13].
Still have questions?
If you'd like help reading a study or a trial listing, email hello@vivonyx.com or use our Ask page. We'll give you a straight answer, including "the research doesn't know yet" when that's the truth.
Related reading
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. Regulatory status can change; check the cited FDA pages for current information. Talk with a qualified, licensed healthcare professional before making any medical decision.
References
American Academy of Orthopaedic Surgeons (OrthoInfo). Meniscus Tears. https://www.orthoinfo.org/diseases--conditions/meniscus-tears/
Whitehouse MR, Howells NR, Parry MC, et al. Repair of torn avascular meniscal cartilage using undifferentiated autologous mesenchymal stem cells: from in vitro optimization to a first-in-human study. Stem Cells Transl Med. 2017;6(4):1237-1248. PMID: 28186682. https://pubmed.ncbi.nlm.nih.gov/28186682/
Olivos-Meza A, Pérez Jiménez FJ, Granados-Montiel J, et al. First clinical application of polyurethane meniscal scaffolds with mesenchymal stem cells and assessment of cartilage quality with T2 mapping at 12 months. Cartilage. 2021;13(1 Suppl):197S-207S. PMID: 31387368. https://pubmed.ncbi.nlm.nih.gov/31387368/
Vangsness CT Jr, Farr J 2nd, Boyd J, et al. Adult human mesenchymal stem cells delivered via intra-articular injection to the knee following partial medial meniscectomy: a randomized, double-blind, controlled study. J Bone Joint Surg Am. 2014;96(2):90-98. PMID: 24430407. https://pubmed.ncbi.nlm.nih.gov/24430407/
Sekiya I, Koga H, Otabe K, et al. Additional use of synovial mesenchymal stem cell transplantation following surgical repair of a complex degenerative tear of the medial meniscus of the knee: a case report. Cell Transplant. 2019;28(11):1445-1454. PMID: 31313604. https://pubmed.ncbi.nlm.nih.gov/31313604/
Sekiya I, Koga H, Katano H, et al. Second-look arthroscopy after meniscus repair and synovial mesenchymal stem cell transplantation to treat degenerative flaps and radial tears of the medial meniscus: a case report. J Orthop Sci. 2022;27(4):821-834. PMID: 34120825. https://pubmed.ncbi.nlm.nih.gov/34120825/
Huang L, Zhang S, Wu J, et al. Immunity-and-matrix-regulatory cells enhance cartilage regeneration for meniscus injuries: a phase I dose-escalation trial. Signal Transduct Target Ther. 2023;8(1):417. PMID: 37907503. https://pubmed.ncbi.nlm.nih.gov/37907503/
Chew E, Prakash R, Khan W. Mesenchymal stem cells in human meniscal regeneration: a systematic review. Ann Med Surg (Lond). 2017;24:3-7. PMID: 29062478. https://pubmed.ncbi.nlm.nih.gov/29062478/
Kader N, Asopa V, Baryeh K, et al. Cell-based therapy in soft tissue sports injuries of the knee: a systematic review. Expert Opin Biol Ther. 2021;21(8):1035-1047. PMID: 33399489. https://pubmed.ncbi.nlm.nih.gov/33399489/
Rinonapoli G, Gregori P, Di Matteo B, et al. Stem cells application in meniscal tears: a systematic review of pre-clinical and clinical evidence. Eur Rev Med Pharmacol Sci. 2021;25(24):7754-7764. PMID: 34982437. https://pubmed.ncbi.nlm.nih.gov/34982437/
Runer A, Kolevar MP, Nazzal EM, et al. Managing the meniscus Part 2: traumatic tear patterns, biologic augmentation, transplantation, innovation and future research. Knee Surg Sports Traumatol Arthrosc. Published online January 31, 2026. doi:10.1002/ksa.70314. PMID: 41618807. https://pubmed.ncbi.nlm.nih.gov/41618807/
Kunze KN, Morgan JT, Gerhold C, et al. An international expert consensus statement defining the best practices and areas of uncertainty concerning the use of orthobiologics. J Bone Joint Surg Am. 2026;108(17):1340-1351. PMID: 42520131. https://pubmed.ncbi.nlm.nih.gov/42520131/
U.S. Food and Drug Administration. Important Patient and Consumer Information About Regenerative Medicine Therapies. https://www.fda.gov/vaccines-blood-biologics/consumers-biologics/important-patient-and-consumer-information-about-regenerative-medicine-therapies
U.S. Food and Drug Administration. Consumer Alert on Regenerative Medicine Products Including Stem Cells and Exosomes. https://www.fda.gov/vaccines-blood-biologics/consumers-biologics/consumer-alert-regenerative-medicine-products-including-stem-cells-and-exosomes
ClinicalTrials.gov (U.S. National Library of Medicine). Search: meniscus, mesenchymal. https://clinicaltrials.gov/search?cond=meniscus&intr=mesenchymal