Comparison of photobiomodulation and anti-inflammatory drugs on tissue repair on collagenase-induced achilles tendon inflammation in rats

by Ingvill Fjell Naterstad, Rafael Paolo Rossi, Rodrigo Labat Marcos, Nivaldo Antonio Parizzoto, Lucio Frigo, Jón Joensen, Patrícia Sardinha Leonardo Lopes Martins, Jan Magnus Bjordal, Rodrigo Alvaro Brandão Lopes-Martins

Background: Tendinopathy is characterized by pain, edema, and structural changes in tendon tissue.

Objective: In this animal study we decided to compare the short- and medium-term effects of low-level laser therapy (LLLT), dexamethasone, and diclofenac on inflammation and tendon tissue repair in collagenase-induced tendinitis.

Results: Collagenase injection induced a severe inflammatory reaction with significant reduction in collagen content for 48 h, and disorientation of collagen fibers lasting between 14 and 21 days. Diclofenac and dexamethasone reduced inflammatory signs during the first 2 days, although there was prolongation of the inflammatory phase and slower normalization of tendon quality, particularly in the dexamethasone group. LLLT prevented hemorrhage, reduced inflammation severity, and preserved tendon morphology compared with the other groups.

Conclusions: LLLT showed a significant superiority over commonly used anti-inflammatory pharmaceutical agents in acute collagenase-induced tendinitis.