Red Light Therapy (RLT), also known as photobiomodulation, is a non-invasive treatment that uses specific wavelengths of light, typically in the red and near-infrared spectrum, to stimulate healing and reduce pain. Tendonitis, a common issue affecting millions, involves pain and dysfunction in the connective tissue linking muscle to bone. This article explores the scientific foundation and clinical evidence supporting the use of RLT for managing tendon issues.
Understanding Tendonitis
The term “tendonitis” is often used broadly, but modern medical understanding refers to a more generalized condition called tendinopathy. Tendinopathy is an umbrella term encompassing various tendon disorders, including true tendonitis (acute inflammation) and tendinosis (non-inflammatory degeneration of the collagen structure). Chronic tendon pain is most frequently a degenerative process, or tendinosis, rather than purely an inflammatory one.
These conditions typically result from repetitive stress, overuse, or a sudden, excessive strain on the tendon. Common areas affected include the Achilles tendon, the rotator cuff in the shoulder, and the tendons around the elbow, often known as “tennis elbow” or “golfer’s elbow.” Symptoms generally include a dull ache, stiffness, tenderness at the site of injury, and reduced strength or mobility.
The pain is often most pronounced during or after activity and can significantly limit daily function and athletic performance. Because tendons naturally have a poor blood supply, their healing process is slow.
The Science Behind Red Light Therapy
The mechanism of RLT centers on its ability to enhance cellular function through photobiomodulation. Specific wavelengths of light, primarily red light (around 630 to 660 nanometers) and near-infrared light (around 810 to 850 nanometers), are absorbed by the body’s cells.
This absorption occurs within the mitochondria, the cell’s powerhouses, specifically targeting an enzyme known as cytochrome c oxidase. When this enzyme absorbs the light photons, it accelerates the electron transport chain, which is the sequence of reactions that generates cellular energy.
The boost in activity leads to increased production of adenosine triphosphate (ATP), the primary energy currency of the cell. Higher ATP levels provide the necessary fuel for cellular repair and enhanced function. RLT also helps displace nitric oxide, which normally inhibits ATP production during cellular stress. By freeing up the enzyme, RLT restores the cell’s ability to create energy efficiently, supporting the reduction of inflammation and tissue regeneration.
Clinical Evidence of Relief and Repair
Research suggests that RLT can be a useful adjunctive therapy for tendinopathy. Studies focusing on common tendon issues, like Achilles and shoulder tendinopathy, often report positive outcomes.
One frequently observed benefit is a reduction in pain scores. This is likely due to the light’s ability to modulate inflammatory pathways and decrease the expression of pro-inflammatory markers, thereby alleviating discomfort associated with the condition.
Beyond pain relief, RLT appears to promote tissue healing by stimulating the activity of fibroblasts, the cells responsible for synthesizing new collagen. This action is particularly relevant for chronic tendinosis, where the tendon tissue has degenerated and requires structural repair. Clinical trials have shown that when RLT is combined with exercise, the combined approach results in greater decreases in pain and improved function compared to exercise alone.
Studies involving Achilles tendinopathy have demonstrated that adding RLT to standard treatment protocols can lead to faster pain relief and better early-stage healing. While the quality of evidence is sometimes noted as low-to-moderate, RLT offers utility as a standalone or complementary treatment for tendon disorders.
Practical Application Guidelines
For individuals considering RLT, attention to the correct application parameters is necessary to maximize the therapeutic effect. Effectiveness depends on delivering the right amount of energy to the target tissue depth.
For tendons, which can be relatively deep, devices should utilize dual wavelengths. Red light (around 660 nanometers) is used for superficial penetration, and near-infrared light (around 850 nanometers) is necessary for deeper tissue reach. Near-infrared light is particularly effective for thicker or deeper tendons, while red light is suitable for more surface-level tendons, such as those in the hand.
Dosage and Duration
The energy density, or dose, is critical. A range of 2 to 20 Joules per square centimeter (J/cm²) per session is often cited as effective in human studies for tendinopathy. The total duration of a session typically lasts between 10 and 20 minutes, depending on the device’s power output and the required dosage.
Treatments are generally recommended three to five times per week to support cellular repair. Higher doses are not always better, as excessive energy can actually reduce the therapy’s effectiveness due to a biphasic dose-response.