Stem cell therapy is a treatment that injects a concentrated solution of bone marrow derive stem cells or other derived stem cells such as those from adipose tissue or fat, into the knee joint. The treatment is designed to address the chronic inflammation that causes much of the pain, protect the existing cartilage from further breakdown, and signal the immune system to initiate a new repair of damaged tissue.

Recent studies: Stem cell therapy for knee pain

An August 2025 study (1) writes: “Regenerative medicine, such as tissue engineering, offers promising solutions (for advanced knee osteoarthritis).” Noting that Mesenchymal stem cell (MSC) intra-articular injections have gained popularity for osteoarthritis management, the study authors compared the therapeutic efficacy of single bone marrow aspirate concentrate (BMAC) and adipose-derived stem cells (ADSCs) injections in knee osteoarthritis patients. Bone marrow aspirate concentrate and adipose-derived stem cells are two of the most used sources of stem cells.

  • 60 patients diagnosed with symptomatic degenerative knee osteoarthritis were enrolled.
  • Patients under 50 received bone marrow aspirate concentrate injections, while those over 50 received adipose-derived stem cells injections.
  • Follow-ups were reported at 1 month, 3 months, and 6 months using the Visual Analog Scale (VAS), WOMAC score, Kellgren-Lawrence classification, and range of motion (ROM).

Results: Both groups showed significant clinical improvements in VAS, WOMAC, and ROM scores with no significant differences between groups. The study  findings indicated that bone marrow samples generally yielded higher MSC counts and showed slightly faster recovery rates among BMAC-treated patients, but with no substantial differences at the 6 month mark.

In a March 2025 study (2), researchers looked at patient data from 502 patients who had not undergone any surgical procedures for knee osteoarthritis. To investigate stem cells, treatment involved intra-articular injections of mesenchymal stem cells without any additional therapy. When compared to the control group, stem cell patients showed a significant improvement in the 6-month WOMAC and the 12-month WOMAC. Mesenchymal stem cells also led to improvements in VAS and KOOS scores at both 6 and 12 months for osteoarthritis patients. Conclusion Intra-articular injections of mesenchymal stem cells alone can significantly alleviate knee pain and dysfunction in patients with untreated osteoarthritis.

How many stem cells? Is there a difference?

A June 2024 study (3) looked for the best bone marrow aspirate concentrate (BMAC) dosage for treating knee osteoarthritis. The study was a prospective controlled dose-escalation trial that included 75 patients with early-stage knee osteoarthritis, divided into three groups based on the bone marrow aspirate concentrate (BMAC) dosage given: 10 × 106 cells (low-dose group), 50 × 106 cells (medium-dose group), or 100 × 106 cells (high-dose group). Each patient received a single intra-articular injection of bone marrow aspirate concentrate (BMAC) and was followed for a year. The main outcomes measured were the Visual Analog Scale (VAS) for pain and the Knee Injury and Osteoarthritis Outcome Score (KOOS) for joint function, recorded at the start, and at 1, 3, 6, and 12 months after the treatment. Any adverse events were also noted.

Results: There were significant improvements in VAS and KOOS scores across all groups at all time points when compared to the baseline. However, these improvements did not show significant differences between the dosage groups during the follow-up. Adverse effects were minimal and mainly included temporary pain and swelling after the injection, with no increase in complications based on the dosage. The absence of significant differences among the various dosages indicates that there may be a limit to the therapeutic benefits beyond a certain point.

An August 2025 (4) systematic review and meta-analysis assessed how effective mesenchymal stem cells  injections are for knee osteoarthritis and to explore the connection between cell dose and treatment results. Data from 300 patients were analyzed. Results showed moderate to large improvement treatment effects. Stem cell doses of 25 million cells or less were linked to a statistically significant improvement, while higher doses did not show any extra benefit.

A January 2020 (5) study from Loughborough University in the United Kingdom suggests:

“Pre-clinical studies have demonstrated successful, safe and encouraging results for articular cartilage repair and regeneration (with intra-articular injections of bone marrow derived mesenchymal stem cells). This is concluded to be due to the multilineage differential potential (this ability to change into different cells allows for tissue repair), immunosuppressive and self-renewal capabilities of bone marrow derived mesenchymal stem cells, which have shown to augment pain and improve functional outcomes. . . Overall, the benefits of intra-articular injections of bone marrow derived mesenchymal stem cells were deemed to outweigh the adverse effects; thus, this treatment be considered as a future therapy strategy. To realise this, long-term large-scale randomised clinical trials are required to enable improved interpretations, to determine the validity of efficacy in future studies.”

A study published in the Archives of orthopaedic and trauma surgery (6) in August 2019 offered these observations on improved outcomes after mesenchymal stem cells injections for knee osteoarthritis: results at 12-months follow-up. This was a systematic review of 18 medical studies and 1069 knees offered treatment.

  • 72% of the included studies harvested the stem cells from the iliac crest (bone marrow-derived MSCs),
  • the remaining 28% from the adipose tissue (adipose-derived MSCs).

The investigators wrote: “According to the current evidences and the main findings of this systematic review, we reported that MSC infiltrations for knee osteoarthritis can represent a feasible option, leading to an overall remarkable improvement of all clinical and functional considered outcomes, regardless of the cell source. Patients treated at earlier-degeneration stages reported statistically significant greater outcomes. The pain and function scores were improved considerably, thus, leading to a significant improvement of patient participation in recreational activities and quality of life.”

A study in the journal Cytotherapy (7) , examined the injection of  mesenchymal stromal cells (bone marrow derived stem cells) as a treatment for knee osteoarthritis.

The study subjects were randomized into two groups:

  • A single injection of stem cells, or
  • A placebo injection of saline solution

Patients were followed up for 6 months after the injection.

Scores were recorded for :

  • Pain level and function improvements to include: walking distance, painless walking distance, standing time and knee flexion compared with the placebo group at 3 and 6 months

The conclusion of this research was the bone marrow derived stem cell injection demonstrated safety and effectiveness. However more research would be needed to confirm this.

Study suggests: Stem Cells Offer Significant Knee Pain Relief

In their 2016 study published in the journal Clinical and translational medicine,(8) researchers at Georgia Regents University wrote: “Current pharmacological treatment strategies are ineffective to prevent the osteoarthritic progression; however, cellular therapies have the potential to regenerate the lost cartilage, combat cartilage degeneration, provide pain relief, and improve patient mobility.” They add that among the cellular therapies, bone marrow-derived stem cells which have been shown to  have a higher chondrogenic capability (the ability to make cartilage) than adipose (fat) derived stem cells, and they have been studied more extensively than the fat derived stem cells.

They also note that: “Due to the increasing incidence and prevalence of osteoarthritis, more innovative and effective therapeutic modalities need to be investigated, including MSCs. More randomized clinical trials need to be completed in order to demonstrate the efficacy, safety, and benefits of MSCs in treating patients with osteoarthritis.”

Stem Cell Institute published research: Short-Term Results of Stem Cell Injections for Knees: Clinical Medicine Insights: Arthritis and Musculoskeletal Disorders

Brent Shaw, Marc Darrow, MD JD : Darrow Stem Cell Institute, Los Angeles, CA, USA
Armen Derian : Mayo Clinic, Phoenix, AZ, USA

`Clinical Medicine Insights: Arthritis and Musculoskeletal Disorders June 18, 2018 (9)

Study synopsis
Preliminary research suggests that bone marrow concentrate (BMC), which contains mesenchymal stem cells and platelets, is a promising treatment for knee osteoarthritis. The aim of this study was to build on this preliminary research by reporting the short-term progress of 15 patients (20 knees) with knee osteoarthritis through 4 BMC (bone marrow derived stem cell treatments.)

The timetable of the four treatments:

  • First treatment
  • Second treatment approximately 14 days after first treatment.
  • Third treatment, approximately 21 days after second treatment, 35 days after first treatment
  • Fourth treatment, approximately 34 days after the third treatment. Approximately 69 days on average after first treatment
  • The last follow-up was conducted a mean 86 days after the first treatment.

What we measured: Overall improvement percentage was compared after each treatment for the following:

  • pain at rest
  • pain during activity
  • functionality scale scores

What we found:

  • Patients experienced statistically significant improvements in active pain and functionality score after the first treatment.
  • Additionally, patients experienced a mean decrease in resting pain after the first treatment, yet outcomes were not statistically significant until after the second treatment.
  • On average, patients experienced:
    • an 84.31% decrease in resting pain,
    • a 61.95% decrease in active pain,
    • and a 55.68% increase in functionality score at the final follow-up.
  • Patients also reported a mean 67% total overall improvement at study conclusion. Outcomes at the final follow-up after the fourth treatment were statistically significant compared to outcomes at baseline, after first treatment, after second treatment, and after third treatment.

In this study we concluded: “These results are promising, and additional research with a larger sample size and longer follow-up is needed to further examine the treatment effectiveness of multiple BMC injections for knee osteoarthritis.”

Is Stem Cell Therapy for Knees Right for You?

Returning to our own published research cited above, I would like to recap the learning points:

  • We found that in the short-term, receiving multiple injections may be more effective than receiving a single Bone Marrow Concentrate stem cell injection.
    • Outcomes at the final follow-up after the fourth treatment were statistically significant compared with outcomes at baseline, after first treatment, after second treatment, and after third treatment.
  • Functionality score increased after first treatment, illustrating that patients experienced an immediate benefit in performing everyday activities with less difficulty.
  • By the second injection, patients began to report improvement with pain at rest. Patients then experienced additional decreases in resting pain with each treatment thereafter.
  • The increase in mean functionality score with successive BMC treatments shows that increasing the number of BMC treatments improves patient performance in daily activities. 

The present findings may provide new clinical insights into treating osteoarthritis with Bone Marrow Concentrate. If Bone Marrow Concentrate treatments become more affordable or covered by insurance companies, there could be an increase in the number of patients receiving multiple Bone Marrow Concentrate treatments for osteoarthritis. If patients who reported improvement to a single injection received multiple, they may experience increased symptomatic relief such as the patients in our study. An additional finding illustrated that patients experienced a greater pain relief when injected with a high-nucleated cell count compared to a lower dose. Our study demonstrates that gradual increase in BMC injections in a short time period may be more effective than a single injection.

We do call on more research to help validate our findings as our small sampling case studies are not definitive.

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References

1 Vitali M, Ometti M, Montalbano F, Spadafora S, Di Micco R, Salini V. Bone Marrow Aspirate Concentrate (BMAC) Versus Adipose-Derived Stem Cells (ADSCs) Intra-articular Injection Therapeutic Efficacy in Knee OA Correlated to Their Mesenchymal Stem Cell (MSC) Cellularity: An Exploratory Comparative Pilot Study. Indian Journal of Orthopaedics. 2025 Dec;59(12):2119-25.
2 Cao M, Ou Z, Sheng R, Wang Q, Chen X, Zhang C, Dai G, Wang H, Li J, Zhang X, Gao Y. Efficacy and safety of mesenchymal stem cells in knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. Stem cell research & therapy. 2025 Mar 7;16(1):122.
3 Muthu S, Ramanathan K, Alagar Yadav S, Jha SK, Ranjan R. Increased cellular dosage of bone marrow aspiration concentrate does not translate to increased clinical effectiveness in knee osteoarthritis: a phase I dose escalation study. Indian Journal of Orthopaedics. 2024 Aug;58(8):1001-8.
4 Rahmadian R, Ariliusra Z, Kusuma KR, Ali H, Raymond B, Meksiko R. Efficacy of a single intra-articular injection of mesenchymal stem cells for knee osteoarthritis: a dose-focused meta-analysis of randomized controlled trials. Journal of Orthopaedic Surgery and Research. 2025 Aug 30;20(1):812.
5 Doyle EC, Wragg NM, Wilson SL. Intraarticular injection of bone marrow-derived mesenchymal stem cells enhances regeneration in knee osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2020 Dec;28(12):3827-42.
6 Migliorini F, Rath B, Colarossi G, Driessen A, Tingart M, Niewiera M, Eschweiler J. Improved outcomes after mesenchymal stem cells injections for knee osteoarthritis: results at 12-months follow-up: a systematic review of the literature. Archives of orthopaedic and trauma surgery. 2019 Aug 27:1-6.
7 Emadedin M, Labibzadeh N, Liastani MG, Karimi A, Jaroughi N, Bolurieh T, Hosseini SE, Baharvand H, Aghdami N. Intra-articular implantation of autologous bone marrow-derived mesenchymal stromal cells to treat knee osteoarthritis: a randomized, triple-blind, placebo-controlled phase 1/2 clinical trial. Cytotherapy. 2018 Oct 11. pii: S1465-3249(18)30605-4. doi: 10.1016/j.jcyt.2018.08.005. PubMed PMID: 30318332.
8 Burke J, Hunter M, Kolhe R, Isales C, Hamrick M, Fulzele S. Therapeutic potential of mesenchymal stem cell based therapy for osteoarthritis. Clinical and Translational Medicine. 2016;5:27. doi:10.1186/s40169-016-0112-7.
9 Shaw B, Darrow M, Derian A. Short-Term Outcomes in Treatment of Knee Osteoarthritis With 4 Bone Marrow Concentrate Injections. Clin Med Insights Arthritis Musculoskelet Disord. 2018 Jun 18;11:1179544118781080. doi: 10.1177/1179544118781080. PMID: 29977117; PMCID: PMC6024328.