OBJECTIVES: Low-level laser therapy (LLLT) is not recommended in major knee osteoarthritis (KOA) treatment guidelines. We investigated whether a LLLT dose-response relationship exists in KOA. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Eligible articles were identified through PubMed, Embase, Cumulative Index to Nursing and Allied Health Literature, Physiotherapy Evidence Database and Cochrane Central Register of Controlled Trials on 18 February 2019, reference lists, a book, citations and experts in the field. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: We solely included randomised placebo-controlled trials involving participants with KOA according to the American College of Rheumatology and/or Kellgren/Lawrence criteria, in which LLLT was applied to participants' knee(s). There were no language restrictions. DATA EXTRACTION AND SYNTHESIS: The included trials were synthesised with random effects meta-analyses and subgrouped by dose using the World Association for Laser Therapy treatment recommendations. Cochrane's risk-of-bias tool was used. RESULTS: 22 trials (n = 1,063) were meta-analysed. Risk of bias was insignificant. Overall, pain was significantly reduced by LLLT compared with placebo at the end of therapy (14.23 mm visual analogue scale (VAS; 95% CI 7.31 to 21.14)) and during follow-ups 1 to 12 weeks later (15.92 mm VAS (95% CI 6.47 to 25.37)). The subgroup analysis revealed that pain was significantly reduced by the recommended LLLT doses compared with placebo at the end of therapy (18.71 mm (95% CI 9.42 to 27.99)) and during follow-ups 2 to 12 weeks after the end of therapy (23.23 mm VAS (95% CI 10.60 to 35.86)). The pain reduction from the recommended LLLT doses peaked during follow-ups 2 to 4 weeks after the end of therapy (31.87 mm VAS significantly beyond placebo (95% CI 18.18 to 45.56)). Disability was also statistically significantly reduced by LLLT. No adverse events were reported. CONCLUSION: LLLT reduces pain and disability in KOA at 4 to 8 J with 785 to 860 nm wavelength and at 1 to 3 J with 904 nm wavelength per treatment spot. PROSPERO REGISTRATION NUMBER: CRD42016035587.
Reproduced with permission from the BMJ Publishing Group.

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