# Optimizing LED photobiomodulation parameters to prevent cartilage matrix degradation in knee osteoarthritis: in vitro and in vivo study

## TL;DR

This study identifies optimal LED therapy parameters that reduce cartilage damage and pain in knee osteoarthritis using in vitro and in vivo experiments.

## Contribution

The study determines that 940 nm LED at 52 J/cm² is most effective in preventing cartilage matrix degradation in knee osteoarthritis.

## Key findings

- 940 nm LED at 52 J/cm² suppressed mmp3/mmp13 and upregulated col2a1/aggrecan in chondrocytes.
- 940 nm LED at 52 J/cm² improved weight-bearing and reduced cartilage degradation in a murine KOA model.
- 940 nm LED at 52 J/cm² inhibited mmp3 and increased collagen II in cartilage tissues.

## Abstract

Photobiomodulation using light-emitting diode (LED) therapy is a promising and safe non-invasive approach for treating knee osteoarthritis (KOA), yet the most effective wavelength and energy density to prevent cartilage matrix degradation remain unclear. This study aimed to determine the optimal LED parameters for suppressing chondrocyte extracellular matrix (ECM) degradation in vitro, and for alleviating ECM degradation and pain-related behaviours in a murine KOA model.

TNF-α-stimulated RCJ 3.1.C5.18 chondrocytes were irradiated with LEDs (625/810/940/1050 nm; 13–78 J/cm2 at 44 mW/cm2). Chondrocyte ECM-related markers (mmp3, mmp13, col2a1, aggrecan) were quantified via RT-qPCR. In vivo, destabilization of the medial meniscus (DMM)-induced KOA mice (n = 5–6/group) received 810 nm (39/52 J/cm2) or 940 nm (39/52 J/cm2) LED therapy thrice weekly for 6 weeks. Pain-like behaviors (Von Frey, incapacitance tests) and histopathology (OARSI scoring, mmp3/collagen II immunofluorescence) were assessed.

In vitro, 940 nm LED at 52 J/cm2 most effectively suppressed mmp3/mmp13 mRNA (P < 0.05) and upregulated col2a1/aggrecan (P < 0.05), while 810 nm at 39 J/cm2 only inhibited mmp3 and mmp13. The LED with 625 nm and 1050 nm showed no significant effect on chondrocyte ECM degradation markers. In vivo, 940 nm at 52 J/cm2 improved weight-bearing asymmetry by 31% at 6 weeks (vs. DMM controls, P = 0.03) and reduced cartilage degradation by 50% (OARSI score, P = 0.03). Immunofluorescence indicated that 940 nm at 52 J/cm2 LED therapy significantly inhibited the expression of mmp3 and increased collagen II protein levels in cartilage tissues.

LED therapy at 940 nm with 52 J/cm2 attenuates ECM degradation and pain in KOA, defining a target LED parameter set for potential clinical translation.

The online version contains supplementary material available at 10.1186/s13018-025-06341-7.