Knee Osteoarthritis and Photobiomodulation: What Recent Studies Show

Knee osteoarthritis, or gonarthrosis, is one of the most common chronic joint conditions in France. Pain when walking, stiffness upon waking, and stairs that have become a daunting challenge: for millions of people, this progressive deterioration of cartilage becomes a daily reality and gradually reduces their quality of life. Given the limitations of conventional anti-inflammatory drugs—whose effectiveness remains partial and which can be difficult to tolerate over the long term—photobiomodulation is attracting growing interest. Here’s what the research really says.

Knee Osteoarthritis: Understanding What Happens in the Joint

Osteoarthritis is not simply a matter of age-related mechanical wear and tear. It is an active process in which inflammation plays a central role. When the cartilage in the knee breaks down, the surrounding cells release pro-inflammatory substances called cytokines, which in turn fuel the destruction of joint tissue. A vicious cycle sets in: pain limits movement, immobility worsens stiffness, and accelerates muscle loss around the joint.

Knee osteoarthritis is characterized by mechanical pain that worsens with activity, joint crepitus, intermittent swelling of the knee, and a gradual loss of range of motion. In some people, chronic pain eventually disrupts sleep and mood, further diminishing quality of life.

The goal is therefore twofold: to reduce inflammation to manage pain, and to preserve joint and muscle function as much as possible. Photobiomodulation (PBM) works precisely along these two lines.

What is photobiomodulation?

Photobiomodulation is a light therapy that uses LED devices or low-power lasers emitting light in the red (630–660 nm) and near-infrared (810–850 nm) wavelengths. These light waves penetrate the skin without causing heat or pain, reaching deep tissues, including muscles, tendons, and the knee joint capsule.

Once absorbed by the mitochondria within cells, this light energy triggers a chain reaction: ATP production increases, available cellular energy rises, and the body’s natural mechanisms for regulating inflammation are activated. This fundamental effect of PBM is referred to as cellular biostimulation.

A useful clarification: conventional light therapy (white-spectrum lamps) targets mood disorders or circadian rhythm disorders. Photobiomodulation, on the other hand, acts on biological tissues via specific wavelengths, producing measurable cellular effects. The two approaches should not be confused.

What studies on knee osteoarthritis show

Research on PBM for knee osteoarthritis has evolved over several decades. The available data, drawn from clinical trials and meta-analyses, now allow for a nuanced yet encouraging assessment.

A significant reduction in chronic pain

Several meta-analyses have reviewed all clinical trials examining the use of therapeutic lasers and LEDs for knee osteoarthritis. Their conclusions are consistent: photobiomodulation helps significantly reduce joint pain compared to a placebo, with measurable effects observed as early as four to six weeks of regular treatment sessions.

A review published in *Photomedicine and Laser Surgery* compiled the results of several randomized controlled trials involving individuals with chronic knee osteoarthritis. Pain relief, assessed using standardized scales, averaged 40 to 50% compared to control groups. Better yet, these results persisted for several weeks after treatment ended, confirming a lasting effect on pain management.

Improved joint mobility and functional recovery

Beyond pain relief, several studies have measured knee range of motion before and after a course of PBM. The results show a significant improvement in joint flexion and extension, as well as a reduction in the duration of morning stiffness—that characteristic symptom that requires “loosening up” the knee before one can walk normally.

Functional recovery is partly due to the effect of infrared waves on the periarticular muscle tissue. By improving microcirculation and reducing muscle tension, light therapy helps restore smoother joint movement, which facilitates the resumption of appropriate physical activity.

Modulation of inflammation at the cellular level

Imaging studies and biological measurements have documented the local anti-inflammatory effects of PBM on the knee joint. Red and infrared light reduces the production of pro-inflammatory cytokines, including interleukin-1β and TNF-α, which are involved in the progressive destruction of articular cartilage. At the same time, it promotes collagen synthesis by synovial fibroblasts, supporting tissue structure and contributing to a gradual reduction in local inflammation.

These cellular processes explain why the effects of PBM develop gradually over several weeks: it does not provide immediate pain relief comparable to that of medication, but rather promotes a slow and lasting regeneration of the joint’s natural mechanisms.

Cryotherapy, physical therapy, and PBM: complementary approaches

Photobiomodulation fits naturally into a comprehensive treatment plan for knee osteoarthritis. It can be combined with local cryotherapy (cold application) to manage acute inflammatory flare-ups, with physical therapy to strengthen the muscles that stabilize the knee, or with sessions of progressive physical rehabilitation.

Many rheumatologists and physical therapists combine PBM and functional rehabilitation, achieving good results in reducing pain and improving joint mobility. The synergy between these approaches often reduces the need for anti-inflammatory medications, resulting in better digestive tolerance for individuals who are sensitive to them.

Important precautions to know before you begin

Photobiomodulation is one of the best-tolerated therapies available for managing chronic joint pain. It does not cause excessive heat, skin irritation, or any documented side effects under normal use. However, there are a few situations that require prior medical consultation:

• Presence of a tumor or a history of cancer in the area to be treated
• Taking photosensitizing medications (certain antibiotics, retinoids, antiepileptic drugs)
• Pregnancy, as a precaution and in the absence of sufficient data in this context
• Photosensitive epilepsy, when using a device in pulsed mode

In all other cases, PBM sessions may be considered without any major contraindications, including in older adults, frail individuals, or those with multiple concurrent joint conditions.

Photobiomodulation: A Practical Approach to Managing Osteoarthritis

Knee osteoarthritis is more than just a damaged joint. It affects mobility, independence, and sometimes even mood and sleep quality. Photobiomodulation does not promise a cure: cartilage does not regenerate on its own. What it offers is a non-invasive, well-documented, and remarkably well-tolerated treatment option to help reduce chronic pain, improve joint recovery, and regain a little more freedom in everyday movements. When used regularly and under appropriate medical supervision, PBM sessions allow many people to get back on their feet—both literally and figuratively.

Also worth reading on The PBM:

• Photobiomodulation: dangers, contraindications and misconceptions
• Portable Photobiomodulation Devices: A Buyer’s Guide
• Best Practices and Safety