Photobiomodulation effects on Achilles tendon pain: a systematic review and meta-analysis of randomized clinical trials

BACKGROUND: Achilles tendon pain is present in tendons’ non-rupture injuries usually exacerbated by mechanical loading (i.e., overuse injury).Photobiomodulation is a light therapy that may reduce pain in tendinopathy. AIM: This systematic review and meta-analysis of randomized clinical trials tested the acute and chronic effects of photobiomodulation on Achilles tendon pain. METHOD: Randomized clinical trials were included comparing photobiomodulation with a control group in patients with Achilles tendon pain.The search included MEDLINE (Pubmed), SCOPUS, EMBASE, Physiotherapy Evidence Database (PEDro), Cochrane Central Register of Controlled Trials (Cochrane CENTRAL), LILACS, and Science Direct databases, and manual search until November 2021.The bias’s risk was assessed by the Cochrane Collaboration bias risk assessment tool and PEDro scale, while the level of evidence strength by the GRADE. Quantitative analysis through meta-analyzes was performed. The protocol was registered (PROSPERO-CRD42018091509). RESULTS: The search yielded 3.239 papers in the seven databases. Five studies were included after screening, eliminating duplicates, and applying eligibility criteria, and three were included in the meta-analysis. The meta-analysis (n=79) showed no photobiomodulation acute and chronic effects compared with control group on Achilles tendon pain (p= 0.45, SMD: 0.28). In the qualitative analysis, three studies showed a high risk, and two studies a low risk of bias in all characteristics. GRADE analysis showed very low- to low-quality evidence of the studies. CONCLUSION: There is no photobiomodulation effect in Achilles tendon pain. Due to the very low and low strength of evidence, new studies with better methodological quality should be conducted to improve the level of evidence.