Stem Cell Therapy for Knee Osteoarthritis: Evidence from 502 Patients Demonstrates Pain Relief at 6 Months and Sustained Symptom Improvement at 12 Months

A research team focusing on the clinical translation of mesenchymal stem cells (MSCs) in musculoskeletal disorders recently published a systematic review and meta-analysis in Stem Cell Research & Therapy (Impact Factor 7.1, JCR Q1). The study, titled “Efficacy and Safety of Mesenchymal Stem Cells in Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials,” evaluates the therapeutic role of MSCs in knee osteoarthritis (KOA).

The findings suggest that MSC therapy significantly improves symptoms in patients with knee osteoarthritis. Higher doses of MSCs may provide greater clinical benefit, although they may also be associated with an increased risk of localized complications. As a result, targeted delivery strategies are identified as a critical direction for future clinical translation and optimization of MSC-based therapies.

Research Background

Global Burden and Clinical Characteristics of Knee Osteoarthritis

Knee osteoarthritis (KOA) is one of the most prevalent degenerative joint disorders worldwide and represents a major contributor to disability across aging populations. Pathologically, KOA is characterized by progressive cartilage degeneration, synovial inflammation, subchondral bone remodelling, and joint space narrowing. Clinically, patients commonly experience chronic joint pain, stiffness, swelling, and reduced mobility, significantly impairing daily functioning and overall quality of life.

Conventional treatment strategies for KOA typically focus on symptom management rather than structural regeneration. These include conservative pharmacological therapies such as nonsteroidal anti-inflammatory drugs (NSAIDs), intra-articular hyaluronic acid injections, and corticosteroid injections, as well as physical therapy and lifestyle modification. In more advanced cases, surgical interventions including total knee arthroplasty may be required. While these approaches may provide temporary pain relief and functional improvement, their ability to restore damaged cartilage or reverse disease progression remains limited.

Regenerative Medicine and the Therapeutic Potential of MSCs

With the rapid advancement of regenerative medicine, mesenchymal stem cells (MSCs) have emerged as a promising therapeutic candidate. MSCs possess multipotent differentiation capacity and can give rise to various cell types, including chondrocytes. Beyond their regenerative potential, MSCs exert immunomodulatory and anti-inflammatory effects, regulate the local microenvironment, and promote tissue repair.

Due to these combined anti-inflammatory and cartilage-regenerative properties, MSC therapy is increasingly being investigated as a novel treatment strategy for osteoarthritis globally. To further clarify the clinical value of MSC therapy, the research team conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the safety and efficacy of intra-articular MSC injections as a standalone treatment for knee osteoarthritis.

Study Design

Study Selection and Patient Population

This study included eight randomized controlled trials (RCTs) published up to August 2024. A total of 502 patients diagnosed with knee osteoarthritis were analyzed. The inclusion criteria required patients to have a confirmed diagnosis of knee osteoarthritis and to have received treatment consisting solely of intra-articular MSC injections under a randomized controlled study design.

Exclusion criteria included patients who had undergone surgical interventions such as total knee replacement, as well as those treated with combination therapies involving bone marrow concentrate, platelet-rich plasma (PRP), or other mixed biological preparations alongside MSCs. By focusing exclusively on standalone MSC injections, the study aimed to isolate and accurately evaluate the independent therapeutic effect of MSC therapy.

Outcome Measures and Evaluation Criteria

The primary outcome measure was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), a widely used clinical assessment tool measuring pain, stiffness, and physical function in osteoarthritis patients.

Secondary outcome measures included the Visual Analog Scale (VAS) for pain assessment, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the incidence of adverse events.

A structured literature selection process was implemented to ensure methodological rigor. Standardized inclusion and exclusion criteria were applied to minimize bias and enhance the reliability and reproducibility of the findings.

Research Results

Overall Clinical Effectiveness

Compared with conventional treatments, MSC therapy demonstrated statistically significant improvements in WOMAC scores at both 6-month and 12-month follow-up periods. These results indicate that MSC injections can provide both short-term and sustained symptom relief in patients with knee osteoarthritis.

Importantly, all three WOMAC subdomains—pain, stiffness, and physical function—showed significant improvement. This suggests that the therapeutic benefits of MSC therapy are not limited to a single symptom dimension but instead reflect a comprehensive improvement in joint condition and patient-reported outcomes.

Dose-Dependent Effects and Safety Considerations

Both high-dose injections, defined as 1.0 × 10⁸ to 2.0 × 10⁸ cells, and low-dose injections, defined as 1.0 × 10⁷ to 6.4 × 10⁷ cells, significantly improved WOMAC scores. However, the high-dose group appeared to demonstrate comparatively greater clinical benefit.

At the same time, higher cell doses may be associated with an increased likelihood of localized complications. Therefore, while dose escalation may enhance therapeutic response, it also underscores the importance of optimizing dosing strategies to balance efficacy and safety. The development of targeted and precision-based delivery systems may further enhance therapeutic outcomes while minimizing risk.

Conclusion and Future Perspectives

This systematic review and meta-analysis provides evidence supporting the safety and efficacy of standalone MSC injections in the treatment of knee osteoarthritis. The findings indicate that MSC therapy may represent a promising regenerative strategy capable of addressing both inflammatory processes and cartilage degeneration.

Higher cell doses may produce stronger therapeutic effects, but careful monitoring is required due to the potential for localized adverse reactions. Consequently, the development of targeted delivery systems and precision dosing strategies is considered a key priority for future clinical translation.

As regenerative medicine continues to expand across international markets, MSC therapy is increasingly being explored in diverse healthcare systems worldwide. Standardization of cell sourcing, manufacturing quality control, regulatory oversight, and long-term outcome assessment will be essential for broader adoption.

Continued large-scale, high-quality randomized controlled trials are needed to further refine treatment protocols, identify optimal patient populations, and determine whether MSC therapy can deliver sustained structural regeneration in addition to symptomatic improvement.