When a bone fracture occurs, whether from a sports injury, accident, or overuse, the road to recovery can be long and challenging. Traditional treatments like rest, immobilization, and physical therapy are foundational, but researchers and clinicians are constantly exploring innovative therapies to accelerate healing and improve outcomes. One such therapy gaining traction is Low-Level Laser Therapy (LLLT), also known as Photobiomodulation Therapy (PBMT). In this blog, we’ll dive into the science behind LLLT, its effects on bone healing, and what recent research tells us about its potential.

What Is Low-Level Laser Therapy (LLLT)?

LLLT is a non-invasive treatment that uses low-power lasers or light-emitting diodes (LEDs) to deliver specific wavelengths of light to target tissues. Unlike high-power lasers used for cutting or ablation, LLLT works through photobiomodulation—stimulating cellular activity without causing thermal damage. The light penetrates the skin and interacts with cells, triggering biological responses that are thought to promote healing, reduce inflammation, and enhance tissue regeneration.

Key parameters of LLLT that influence its effectiveness include wavelength, energy density, power density, and irradiation frequency. Common wavelengths used in bone healing studies range from 780 nm to 830 nm, with energy densities often around 4 J/cm² and power densities of 100 mW/cm² (Hazrati et al., 2025). These parameters can vary based on the target tissue, fracture type, and animal or human model.

The Science Behind LLLT and Bone Healing

Bone healing is a complex process involving inflammation, angiogenesis (new blood vessel formation), osteogenic differentiation (stem cells becoming bone-forming cells), and mineralization. LLLT is believed to interfere with multiple stages of this process by activating specific molecular pathways.

A 2023 systematic review by Berni et al. highlighted that LLLT promotes angiogenesis, fracture healing, and osteogenic differentiation of stem cells. The review identified key molecular pathways activated by LLLT, including those involving vascular endothelial growth factor (VEGF), fibroblast growth factors (FGF), bone morphogenetic proteins (BMPs), and mitogen-activated protein kinase (MAPK). These pathways play critical roles in stimulating cell proliferation, blood vessel growth, and the production of bone-specific proteins like collagen type 1 and osteocalcin (Berni et al., 2023).

In vitro studies further support these findings. A comparative review by Bayat et al. (2018) analyzed 75 studies on LLLT and low-intensity pulsed ultrasound (LIPUS) and found that LLLT effectively biostimulates osteoblasts (bone-forming cells) and osteocytes (mature bone cells). It enhances osteoblast proliferation and differentiation in various bony cell lines, making it a promising tool for bone regeneration therapy. Additionally, LLLT increases the initial number of stem cells before differentiation, which can boost the number of specialized cells available for tissue repair (Bayat et al., 2018).

Clinical and Preclinical Evidence: What Do the Studies Show?

Research on LLLT for bone healing spans preclinical (animal) and clinical (human) studies, with varying but largely positive outcomes.

Preclinical Studies

A 2025 systematic review and meta-analysis by Hazrati et al. evaluated 27 animal studies (17 on rabbits, 10 on rats) to assess the impact of PBMT on fracture healing. The most common fracture sites were the tibia, femur, mandible, and radius, with 780 nm, 808 nm, and 830 nm lasers being the most frequently used. While most individual studies reported a positive effect of PBMT on fracture healing, the meta-analysis found no significant impact on maximum fracture force or hydroxyapatite Raman peaks (a marker of mineralization). The authors noted that despite this, PBMT still shows potential for enhancing healing, and further research is needed to clarify its effects on specific aspects of bone repair (Hazrati et al., 2025).

Clinical Studies

In human trials, LLLT has shown promising results for stress fractures—a common overuse injury. A prospective randomized trial by Chauhan et al. (2006) investigated LLLT for tibial stress fractures in 68 patients (34 in the treatment group, 34 in the placebo group). The treatment group received LLLT, while the control group received a placebo. The study found that the LLLT group experienced earlier resolution of pain and tenderness, as well as a return to painless ambulation, with fewer recurrences. The authors concluded that LLLT is beneficial for treating tibial stress fractures, though they emphasized the need for larger multicenter studies to confirm these findings (Chauhan et al., 2006).

Why the Discrepancies? Factors Influencing LLLT Efficacy

While the evidence is promising, inconsistencies in study results—such as the lack of significant mineralization effects in Hazrati et al.’s meta-analysis—highlight the need to consider factors that influence LLLT’s efficacy. These include:

• Treatment Parameters: Wavelength, energy density, and irradiation frequency can vary widely between studies, leading to different outcomes. Optimal parameters for specific fracture types and patient populations have not yet been standardized.
• Study Design: Differences in animal models, fracture severity, and assessment methods (radiography, histology, mechanical testing, spectroscopy) can affect results. Human trials are often smaller in scale, making it harder to draw definitive conclusions.
• Cellular Heterogeneity: LLLT’s effects vary by cell type, with stem cells, osteoblasts, and osteocytes responding differently to light stimulation (Berni et al., 2023). This complexity may explain why some studies show stronger effects than others.

The Future of LLLT in Bone Healing

LLLT holds great potential as an adjunctive therapy for bone fracture healing, particularly for stress fractures and cases where healing is delayed. Its non-invasive nature, lack of significant side effects, and ability to stimulate cellular processes critical to bone repair make it an attractive option for clinicians.

To fully realize its potential, future research should focus on:

• Standardizing treatment parameters to optimize efficacy.
• Conducting larger, multicenter human trials to confirm clinical benefits.
• Exploring the mechanisms underlying LLLT’s effects on mineralization and fracture strength.
• Investigating combinations of LLLT with other therapies (e.g., stem cell therapy, ultrasound) to enhance healing outcomes.

Conclusion

Low-Level Laser Therapy (LLLT) is a promising non-invasive treatment for bone fracture healing. Preclinical and clinical studies have shown that it can stimulate angiogenesis, osteogenic differentiation, and symptom resolution—particularly for stress fractures. While meta-analyses have highlighted some inconsistencies, the overall body of evidence supports LLLT’s potential as an adjunct to traditional treatments. As research continues to refine treatment protocols and clarify its mechanisms of action, LLLT may become a standard part of fracture care, helping patients recover faster and more effectively.

References

1. Berni, M., Brancato, A. M., Torriani, C., Bina, V., Annunziata, S., Cornella, E., et al. (2023). The Role of Low-Level Laser Therapy in Bone Healing: Systematic Review. International Journal of Molecular Sciences, 24(8), 7094. https://doi.org/10.3390/ijms24087094
2. Bayat, M., Virdi, A., Rezaei, F., & Chien, S. (2018). Comparison of the in vitro effects of low-level laser therapy and low-intensity pulsed ultrasound therapy on bony cells and stem cells. Progress in Biophysics and Molecular Biology, 133, 36–48. https://doi.org/10.1016/j.pbiomolbio.2017.11.001
3. Chauhan, A., & Sarin, P. (2006). Low Level Laser Therapy in Treatment of Stress Fractures Tibia: A Prospective Randomized Trial. Medical Journal Armed Forces India, 62(1), 27–29. https://doi.org/10.1016/S0377-1237(06)80148-6
4. Hazrati, P., Azadi, A., Fekrazad, S., Wang, H.-L., & Fekrazad, R. (2025). The effect of photobiomodulation therapy on fracture healing: a systematic review and meta-analysis of animal studies. Lasers in Medical Science. https://doi.org/10.1007/s10103-025-04376-0