Oliveira S et al. - Photobiomodulation and Knee Osteoarthritis

In people with knee osteoarthritis, photobiomodulation reduces pain at rest compared with a placebo, with an effect described as moderate but very low certainty of evidence. No significant effect was detected on the Timed Up and Go test, and the authors do not recommend its use on its own.

What this study measured

This publication is a systematic review with a meta-analysis, not a single clinical trial. The authors searched PubMed, EMBASE, Web of Science, and the Cochrane databases through October 2023, selecting only randomized trials comparing photobiomodulation with a placebo in patients with knee osteoarthritis. Study characteristics, intervention parameters, and outcome measures were extracted. Risk of bias was assessed using the Cochrane Randomized Trials Tool, Version 2, and the certainty of the results was assessed using the GRADE approach. Ten studies, totaling 542 participants, were included.

Key Findings

The values below are those published in the abstract. The pain scale used for the combined difference is not specified there.

• Pain at rest, 6 studies: a difference of -0.7 (95% CI: -1.1 to -0.2) in favor of photobiomodulation, an effect classified as moderate
• Certainty of evidence for this result: very low, according to GRADE
• Timed Up and Go Test, 3 studies: no significant effect detected
• Statistically significant intragroup improvement with photobiomodulation in pain, the Lequesne index, and walking performance
• These intra-group improvements are not always clinically relevant or significant when compared with placebo
• All of the included studies have a risk of bias rated as uncertain to high

How photobiomodulation works for this indication

The proposed mechanisms are based on hypotheses derived from basic research and are not evaluated in this review. Red and near-infrared wavelengths are thought to be absorbed by mitochondrial cytochrome c oxidase, which could increase ATP synthesis in the exposed periarticular tissues. This metabolic boost would be accompanied by a modulation of local inflammation, a recognized component of the pathophysiology of osteoarthritis. Finally, an effect on pain transmission pathways could contribute to the observed reduction in pain intensity at rest. None of these mechanisms has been measured in this study; they are discussed in the conditional tense.

Limits You Should Know

The main limitation relates to the quality of the evidence. All included studies have an uncertain to high risk of bias, and the certainty of evidence for pain at rest is very low according to GRADE. The finding regarding the Timed Up and Go test is negative: no significant effect was detected for this functional outcome, based on only three studies. The improvements observed within the treatment group do not consistently translate into a clinically meaningful difference compared with placebo. The authors conclude that this level of certainty does not support recommending photobiomodulation as a stand-alone treatment and call for more rigorous trials as well as a review of dosimetry recommendations.

What This Means in Practice

The authors position photobiomodulation as a potential adjunct to therapies already widely recommended for knee osteoarthritis, rather than as an alternative. Appropriate exercise, weight management, and medical follow-up remain the established treatment approaches. Anyone affected should seek a diagnosis and discuss their options with a healthcare professional.

Frequently Asked Questions

Can photobiomodulation replace my treatment for osteoarthritis?

No. The authors note that the very low certainty of the evidence does not support recommending photobiomodulation as a stand-alone treatment. They present it as a potential adjunct to therapies that are already recommended. Any change in treatment should be discussed with a healthcare professional.

Does it improve mobility and walking?

The results are mixed. No significant effect was detected on the Timed Up and Go test in the three studies analyzed. Improvements in walking performance were indeed observed within the treatment group, but they are not always clinically relevant when compared to the placebo.

What camera settings were used in these tests?

The abstract states that the intervention parameters were collected, but it does not specify the wavelengths, doses, or number of sessions. The authors also emphasize the need to revise the dosimetry recommendations. Therefore, no specific protocol can be inferred from this information.

Reference

Oliveira S, Andrade R, Valente C, Espregueira-Mendes J, Silva FS, Hinckel BB, Carvalho Ó, Leal A. Effectiveness of Photobiomodulation in Reducing Pain and Disability in Patients With Knee Osteoarthritis: A Systematic Review With Meta-Analysis. Physical Therapy, 2024. PMID 38775202. DOI 10.1093/ptj/pzae073. https://doi.org/10.1093/ptj/pzae073

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.