Physical laser therapy, most accurately termed Photobiomodulation (PBM) therapy, is a non-invasive therapeutic modality that uses specific wavelengths of light (typically red and near-infrared) to stimulate cellular function, reduce pain, and accelerate tissue healing . Formerly known as low-level laser therapy (LLLT) or cold laser therapy, this technology has evolved significantly over the past few decades and is now widely used in physiotherapy, sports medicine, and dermatology for a diverse range of conditions.
The fundamental principle of photobiomodulation involves the absorption of photons by endogenous photoreceptors within cells. The primary target is cytochrome c oxidase (COX) , a key enzyme in the mitochondrial respiratory chain responsible for cellular energy production . When red light (620-700 nm) or near-infrared light (700-1440 nm) is applied to tissue, photons are absorbed by COX . This absorption triggers a cascade of cellular events:
• Increased ATP Production: Activation of COX enhances mitochondrial metabolism, leading to a significant increase in adenosine triphosphate (ATP) synthesis . This provides cells with more energy to perform their functions, particularly repair and regeneration.
• Modulation of Reactive Oxygen Species (ROS): PBM induces a brief, low-level generation of ROS, which acts as a signaling molecule to activate protective and reparative cellular pathways .
• Calcium Signaling: The therapy alters intracellular calcium levels, further promoting the activation of various transcription factors and signaling pathways involved in cell proliferation, migration, and differentiation .
• Anti-inflammatory and Analgesic Effects: These cellular changes lead to downstream effects, including the reduction of pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6) and the modulation of pain perception . For example, research has shown that laser irradiation can alleviate osteoarthritis pain by inhibiting spinal microglial activation-mediated neuroinflammation and by activating the spinal adenosine A1 receptor, which helps suppress pain signaling .
The therapeutic effect is dependent on specific treatment parameters, including wavelength, fluence (energy density), treatment duration, and output power . Near-infrared light, in particular, offers superior tissue penetration, allowing for non-invasive treatment of deep tissues such as muscles, tendons, and even the brain .
Physical laser therapy (PBM) has a broad spectrum of clinical applications, supported by a growing body of preclinical and clinical evidence.
PBM is highly effective for treating a variety of painful musculoskeletal conditions:
• Tendinopathies: A significant body of evidence supports the use of low-level laser therapy for chronic tendinopathy. A 2025 systematic review with meta-analysis found that LLLT provides superior pain relief compared to minimal intervention in chronic tendon conditions, with a greater number of treatment sessions associated with a larger extent of pain relief . Preclinical studies confirm that photobiomodulation can enhance tendon structure and function, improving the regeneration process .
• Osteoarthritis (OA): Laser therapy has been shown to alleviate pain in knee osteoarthritis. Studies in animal models demonstrate that laser irradiation can reduce pain by inhibiting neuroinflammation in the spinal cord and activating analgesic pathways .
• Musculoskeletal Pain: A meta-analysis of laser auriculotherapy (applying laser to specific points on the ear) for musculoskeletal pain management demonstrated a significant reduction in pain intensity post-treatment compared to placebo, reflecting a large effect size .
PBM is renowned for its ability to accelerate wound healing and tissue repair:
• Chronic Wounds: By enhancing ATP production, reducing inflammation, and supporting cell growth and proliferation, PBM is used to treat chronic wounds, including diabetic foot ulcers .
• Tendon and Soft Tissue Repair: Preclinical research confirms that photobiomodulation, particularly at wavelengths like 660 nm, can accelerate and improve the tendon regeneration process . It promotes collagen synthesis and reduces inflammatory cells in injured tissues.
The ability of near-infrared light to penetrate deeply into biological tissues opens up applications in neurology:
• Neurological Disorders: PBM has shown promising neuroprotective effects in preclinical models of central nervous system diseases. It is being investigated for its potential to improve brain function in conditions such as Alzheimer's disease, help with movement problems in Parkinson's disease, and ameliorate mental disorders in individuals with depression . By enhancing blood flow and reducing inflammation in the brain, it may offer a novel approach to managing these conditions.
• Diabetic Complications: Beyond wound healing, PBM is being explored for its efficacy in managing other complications of diabetes mellitus, including diabetic peripheral neuropathy and diabetic periodontitis.
