INTRODUCTION: Low-level laser therapy (LLLT) was introduced as an alternative non-invasive treatment for osteoarthritis, but its effectiveness is still controversial. The main objective of this article was to determine the safety and efficacy of LLLT in patients with knee osteoarthritis (KOA). METHODS: In order to gather evidence, main medical databases as well as relevant websites were browsed without time limit. We searched with appropriate keywords and strategies. After quality assessment of studies, study data were extracted by two reviewers. Standard mean difference proposed through inverse variance was used in the meta-analysis using the random-effects model. Twelve values were used for the evaluation of heterogeneity. RESULTS: A total of 823 studies, 14 randomized controlled trials (RCTs) were selected after final review. There was a significant difference between LLLT and placebo in pain at rest (p = 0.02), pain at activity (p = 0.01), total pain (p = 0.03), WOMAC function (p = 0.01), WOMAC stiffness (p = 0.02) and WOMAC total (p < 0.0001) in favor of the LLLT. There was no significant difference between LLLT and placebo in WOMAC pain (p = 0.09) and range of motion (p = 0.1). CONCLUSION: In spite of some positive findings, this meta-analysis lacked data on how LLLT effectiveness is affected with important factors: wavelength, energy density, treatment duration, numbers of sessions the treatment, severity of KOA and site of application.

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