Shedding Low-Level Laser Light on Knee OA

This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.

Low-level laser therapy (LLLT) has been used in multiple countries to treat the pain and function deficits associated with knee osteoarthritis (OA). The wavelength typically used is in the near-infrared region. However, this therapy is not recommended by most clinical guidelines, including those of the Osteoarthritis Research Society International. The hesitancy to recommend LLLT is due largely to conflicting published findings and unresolved dose-related issues such as wavelength, intensity, and frequency of treatment. For treating knee OA, the World Association for Laser Therapy (WALT) recommends applying four times the laser dose with continuous rather than pulsed irradiation.

To try to resolve conflicting evidence, Stausholm et al. conducted a systematic review and meta-analysis of randomized, placebo-controlled trials of LLLT, distilling 22 trials from 2,735 initially identified articles.¹ Pain, as measured by a 0 to 100 mm visual analog scale (VAS), was significantly reduced by LLLT compared with placebo at the end of therapy (14.23 mm 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). Subgroup analysis revealed that pain was significantly reduced by the recommended LLLT doses compared with placebo at the end of therapy (18.71 mm VAS; 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).

Pain reduction from the recommended doses peaked during follow-ups 2 to 4 weeks after the end of therapy. Disability was also significantly reduced by LLLT, and no adverse events were reported in any of the studies. Notably, in light of JBJS Editor-in-Chief Marc Swiontkowski’s recent comments about the quality of meta-analyses, this meta-analysis was reported in accordance with PRISMA guidelines and all included trials were evaluated for risk of bias.

What remains unclear is how far past the skin the varied wavelengths and intensities (usually 1 to 8 Joules) of laser energy penetrate. Likewise, tissue heating has not been measured or analyzed. Still, at present, it appears that LLLT used with WALT guidelines is a safe and potentially effective treatment for the pain and dysfunction of knee OA.

Reference

1. Stausholm MB, Naterstad IF Msc, Joensen J, Lopes-Martins RÁB, Sæbø H Msc, Lund H, Fersum KV, Bjordal JM. Efficacy of low-level laser therapy on pain and disability in knee osteoarthritis: systematic review and meta-analysis of randomised placebo-controlled trials. BMJ Open. 2019 Oct 28;9(10):e031142. doi: 10.1136/bmjopen-2019-031142. PMID: 31662383