Effects of Photobiomodulation on Osteoarthritis from In Vivo and In Vitro Studies: A Narrative Review

Kunimatsu R, Nakatani A, Sakata S, Tanimoto K · International Journal of Molecular Sciences

A review confined to basic research. The mechanisms it assembles are pain inhibition, suppression of inflammatory cytokine production, promotion of anti-inflammatory cytokine and extracellular matrix production, and suppression of the enzymes that degrade that matrix. The authors report that although many studies demonstrate efficacy, only a few have examined intracellular signalling in chondrocytes in any detail, and that the pathways established in other cell types — MAPK/ERK, JNK/AP-1 and Akt — have not been shown to operate in chondrocytes.

Population

Cell and animal studies of photobiomodulation in osteoarthritis, covering both the knee and the temporomandibular joint

Intervention

Low-power laser therapy across a heterogeneous range of parameters

Comparator

Untreated or sham-irradiated osteoarthritis models

Limitations

Basic research only — no human clinical evidence is assessed. The authors state that laser parameters were so heterogeneous across the studies reviewed that rigorous comparison between them is not possible, and that the existing animal studies run 8 weeks or less and therefore cannot speak to the structural progression of osteoarthritis. Pain is largely unevaluated in the models collected, which measure local inflammation and matrix markers. A substantial share of the review concerns the temporomandibular joint, where the authors say basic studies are scarce and where anatomy makes the optimal irradiation conditions likely to differ from the knee. Japanese public funding (JSPS Grants-in-Aid); the authors declare no conflicts of interest.