An educational review based on evidence available through 2026
Hamstring injuries are common in people who participate in sports, particularly activities that involve high-speed running. They do not all follow the same course: a mild strain may resolve within a few weeks, whereas a more extensive tear can cause persistent pain, limit performance, and delay return to activity. There is also a risk of reinjury after returning to sport.¹
In this context, biological therapies such as platelet-rich plasma (PRP) and mesenchymal stromal cells (MSCs) have attracted growing interest. Their study is part of the broader development of regenerative medicine, but two separate questions need to be considered: whether there is a biological rationale for investigating them, and whether a clinical benefit has actually been demonstrated in patients. For hamstring injuries, those two questions do not yet have the same answer.
So, what do we currently know about MSCs in this type of injury?
What is a Hamstring Injury?
The hamstrings are a group of three muscles located at the back of the thigh. They contribute to hip extension and knee flexion and are heavily involved in walking, running, jumping, and particularly explosive movements.
Hamstring injuries commonly occur during high-speed efforts, acceleration, or sudden movements. Their severity varies, ranging from limited involvement of muscle fibers to more extensive structural tears.¹
The clinical history and physical examination guide the diagnosis. Ultrasound and magnetic resonance imaging are not required in every case, but they can be useful when the location or extent of the injury needs to be defined more precisely and, in selected situations, may provide prognostic information.²
Management is determined by the severity of the injury, its clinical course, and the individual’s functional needs. In general, progressive rehabilitation, strengthening, and a gradual return to running and sport-specific movements remain the mainstays of treatment.¹
What are mesenchymal stromal cells?
In the scientific literature, the term mesenchymal stromal cells (MSCs) is frequently used for cells that are also commonly referred to as “mesenchymal stem cells.”
These cells can be obtained from different tissues and are being investigated for their biological properties and potential applications in several areas of regenerative medicine.
A widely circulated explanation suggests that, once administered, MSCs transform into the cells needed by the injured tissue and rebuild it. This does not accurately reflect current understanding and oversimplifies a much more complex process.
Research suggests that some of their potential effects may depend on the release of bioactive molecules, paracrine signaling, interactions with immune cells, and changes in the local tissue microenvironment.³˒⁴
These findings help explain why MSCs remain an active area of research. Even so, observing a plausible mechanism in the laboratory is not the same as demonstrating that an intervention improves a patient’s recovery.
Can MSCs accelerate recovery from a hamstring injury?
Based on the available evidence, it cannot be concluded that MSCs accelerate recovery from hamstring injury, reduce recurrence, or produce a clinically meaningful improvement in function. High-quality clinical studies directly addressing these questions are still lacking.
A recent review of orthobiologics in muscle injury describes this gap clearly: preclinical research is available and interest in PRP and MSCs is increasing, but high-level clinical evidence remains limited.⁵
A review published in 2023 reached a similar conclusion. Basic research involving cellular therapies and PRP has progressed, but studies conducted in patients are far fewer and still do not support firm conclusions.⁶
The uncertainty is not limited to muscle injuries. A 2025 analysis of MSC use in trauma and orthopaedics found substantial differences among studies in indications, cell source, and dose. In addition, only a proportion of completed trials had reported their results in peer-reviewed publications.⁷
For that reason, findings from osteoarthritis, tendon or ligament injuries, and other musculoskeletal conditions cannot simply be extrapolated to hamstring injuries.
What about platelet-rich plasma (PRP)?
PRP has been studied clinically in muscle injury more extensively than MSCs, although this does not mean that its role has been established in every clinical setting.
A recent meta-analysis specifically evaluated PRP for hamstring injuries.⁸ The included studies, however, differed in product preparation, treatment protocols, injury characteristics, and rehabilitation programs. This variability means that the findings need to be interpreted with caution.
In clinical practice, the decision to use PRP should not be based solely on a diagnosis of “hamstring injury.” The type of injury, stage of recovery, previous treatments, and individual patient characteristics should all be considered.
What remains the cornerstone of treatment?
Rehabilitation remains the foundation of treatment for most hamstring injuries.
Depending on the individual case, a rehabilitation program may include progressive strengthening, eccentric exercises, loading at longer muscle lengths, lumbopelvic control, graded running progression, and gradual reintroduction of sport-specific demands.¹
Recovery is also not simply a matter of stopping activity until all pain has disappeared. In a randomized clinical trial, exercising within a controlled pain threshold did not shorten the time to return to sport, although some favorable differences in strength and muscle architecture were observed.⁹
Progression should therefore be tailored to the injury, the patient’s response to exercise, and individual functional goals.
There is also insufficient clinical evidence to support the claim that an intravenous MSC infusion specifically targets an injured hamstring or accelerates its recovery.
MSCs have immunomodulatory and paracrine properties that are being actively investigated, but these experimental mechanisms alone do not establish a localized clinical benefit after intravenous administration.
Accordingly, stating that an intravenous infusion “finds” the injury, regenerates the muscle, or specifically reduces inflammation in the injured hamstring would go beyond what the current clinical evidence supports.
Safety depends on several factors, including the source and characteristics of the cellular product, how it is processed, the dose, the route of administration, and the clinical condition of the person receiving it.
Safety data obtained with one specific product or protocol should not be generalized to all MSC preparations or to different indications.
Potential events to consider include administration-related reactions, local complications, infection or product contamination, and inflammatory or immune responses. In addition, long-term follow-up data remain limited for several cellular interventions.¹⁰
The International Society for Stem Cell Research (ISSCR) distinguishes interventions that remain under investigation from those whose safety and efficacy have been established through a formal clinical development process.
Its guidelines state that new cell-based interventions should be evaluated in appropriately designed clinical studies and within the relevant regulatory framework before being incorporated into standard clinical care.¹¹
The ISSCR patient guide emphasizes another important point: a convincing biological rationale or favorable testimonials do not replace evidence obtained through controlled clinical research.¹²
This is an area of genuine research interest, but important questions remain unanswered.
Researchers are currently studying how MSCs and other biological products may influence processes such as inflammation, fibrosis, and muscle repair.
The challenge is to demonstrate that effects observed in experimental models translate into meaningful benefits for patients, with a clinically relevant magnitude of effect and an acceptable safety profile.
For hamstring injuries, the clinical evidence available through 2026 still does not support considering MSCs an established effective treatment. Progressive rehabilitation, by contrast, has substantially stronger clinical support.¹˒⁵˒⁶
MSCs remain a reasonable field of investigation. Defining their role will require clinical trials using well-characterized products, reproducible protocols, appropriate comparator groups, and adequate follow-up.
Conclusion
MSCs have biological properties that justify their study in regenerative medicine and across a range of musculoskeletal conditions. For hamstring injuries, however, clinical research remains insufficient to establish a clear therapeutic benefit.
Biological potential to support tissue repair and demonstrated clinical benefit are two different questions.
At present, there is no high-quality clinical evidence showing that MSCs regenerate injured hamstring muscle, shorten the time to return to sport, or reduce the risk of another hamstring injury.
If a regenerative intervention is being considered, the decision should begin with an individualized medical assessment and a clear discussion of the available alternatives, potential risks, uncertainties, and quality of the evidence. At present, rehabilitation remains the reference standard for management.
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Educational note: This content is intended for educational purposes and does not replace an individualized medical assessment. Treatment decisions should be made on a case-by-case basis, taking into account the diagnosis, available alternatives, risks, potential benefits, quality of the evidence, and applicable regulations. |
Speak to Stemwell today to find out more
Stem cell therapy represents an exciting new treatment avenue for hamstring injuries, with the potential to promote quicker healing and improve your overall quality of life. Our expert team at Stemwell are dedicated to supporting you and finding the right treatment option to meet your needs.
If you would like to find out more about stem cell therapy you can contact us with any questions, or apply today to check your eligibility.
References
References verified in PubMed and official institutional sources. DOI/PMID is included when available, together with an access link to facilitate consultation.
1. Hickey JT, Opar DA, eiss LJ, Heiderscheit BC. Hamstring strain injury rehabilitation. J Athl Train. 2022;57(2):125-135. doi:10.4085/1062-6050-0707.20. PMID:35201301. Available from: PubMed
2. Hollabaugh WL, Sin A, Walden RL, Weaver JS, Porras LP, LeClere LE, et al. Outcomes of activity-related lower extremity muscle tears after application of the British Athletics Muscle Injury Classification: a systematic review. Sports Health. 2024;16(5):783-796. doi:10.1177/19417381231195529. PMID:37681683. Available from: PubMed
3. Laumonier T, Menetrey J. Muscle injuries and strategies for improving their repair. J Exp Orthop. 2016;3(1):15. doi:10.1186/s40634-016-0051-7. PMID:27447481. Available from: PubMed
4. Torres-Torrillas M, Rubio M, Damia E, Cuervo B, Del Romero A, Pelaez P, et al. Adipose-derived mesenchymal stem cells: a promising tool in the treatment of musculoskeletal diseases. Int J Mol Sci. 2019;20(12):3105. doi:10.3390/ijms20123105. PMID:31242644. Available from: PubMed
5. Droz LG, Blaber OK, Hurley ET. Orthobiologics in muscle injury. Clin Sports Med. 2025;44(4):735-747. doi:10.1016/j.csm.2024.10.005. PMID:41101907. Available from: PubMed
6. Stephens PM, Nussbaum RP, Onishi K. Orthobiologic interventions for muscle injuries. Phys Med Rehabil Clin N Am. 2023;34(1):181-198. doi:10.1016/j.pmr.2022.08.012. PMID:36410882. Available from: PubMed
7. Bezuglov E, Dolgalev I, Kuznetsova M, Zholinskiy A, Savin E, Goncharov E, et al. Mesenchymal stem cells injections in traumatology and orthopaedics: common practice or still a promising area with many uncertainties? BMC Musculoskelet Disord. 2025;26(1):840. doi:10.1186/s12891-025-09123-8. PMID:40898126. Available from: PubMed
8. Liu M, Zhai H, Wang R, Wang J, Xiong Y, Peng Y. Effect of platelet-rich plasma injection in hamstring injury: a systematic review and meta-analysis. J Sport Rehabil. 2026;35(2):98-105. doi:10.1123/jsr.2024-0278. PMID:40615116. Published online 2025 Jul 23; print issue 2026. Erratum: J Sport Rehabil. 2026;35(2):164. doi:10.1123/jsr.2025-0264. Available from: PubMed
