In Vitro and In Vivo Effects of Light Therapy on Cartilage Regeneration for Knee Osteoarthritis: A Systematic Review

Oliveira S, Andrade R, Hinckel BB, Silva F, Espregueira-Mendes J, Carvalho Ó, Leal A · Cartilage

Light therapy reduced extracellular matrix degradation, inflammation and osteoarthritis progression and promoted matrix synthesis, and improved pain-like behaviour in animals with no apparent effect on gait. Findings conflicted on some biochemical, histological and behavioural outcomes. More than a quarter of the studies delivered energy per point below the World Association for Laser Therapy minimum of 4 J plus or minus 50 percent, some as low as 0.3 J and 1.4 J, and several of those were among the studies showing no effect on matrix synthesis, no downregulation of MMPs and no histological improvement. Studies using the lower doses generally needed more than 20 sessions before any outcome separated. Combining light therapy with exercise or with topical NSAIDs added nothing over light therapy alone; combining it with intra-articular stem cells or with chondroitin and glucosamine sulfate enhanced the effect on cartilage.

Population

3 in vitro studies and 30 in vivo animal studies of light therapy on knee cartilage in osteoarthritis models, searched across PubMed, Embase, Scopus and Web of Science to 31 August 2020

Intervention

Light therapy — red and near-infrared lasers (600-1100 nm), one He-Ne, one InGaAlP, one LED, and two carbon-dioxide laser acupuncture studies

Comparator

Sham or untreated osteoarthritis controls; some studies also compared light therapy against or alongside exercise, topical NSAIDs, stem-cell injection, and chondroitin with glucosamine

Limitations

No human clinical evidence: the review covers in vitro and animal work only, and excluded inflammatory and rheumatoid arthritis models by design. Performance and detection bias were judged high risk for every included study, which the authors say limits the strength of the conclusions. Inconsistent outcome reporting prevented a meta-analysis, and only three in vitro studies were found at all. The WALT dose guidance the authors measure the studies against is itself valid only for GaAs and GaAlAs lasers, not for He-Ne, InGaAlP or LEDs. Portuguese public funding (FCT), stated as not involved in design, interpretation or publication; the authors declare no conflicts.