Biomechanical and biochemical protective effect of low-level laser therapy for Achilles tendinitis

Abstract

For three decades, low level laser therapy (LLLT) has been used for treatment of tendinitis as well as other musculoskeletal diseases. Nevertheless, the biological mechanisms involved remain not completely understood. In this work, the effects of LLLT and of the widely used nonsteroidal anti-inflammatory drug, diclofenac, have been compared in the case of collagenase-induced Achilles tendinitis. Wistar rats were treated with diclofenac or laser therapy. The tensile behavior of tendons was characterized through successive loading-unloading sequences. The method considered 11 characteristic parameters to describe the mechanical behavior. It was shown that during the acute inflammatory process of the tendon, the mechanical properties were significantly correlated to the high levels of MMP-3, MMP-9 and MMP-13 expression presented in a previous paper (Marcos, R.L., et al., 2012). The treatment by non-steroidal anti-inflammatory drugs such as diclofenac sodium produces a low protective effect and can affect the short-term biochemical and biomechanical properties. On the contrary, it is shown that LLLT exhibits the best results in terms of MMPs reduction and mechanical properties recovery. Thus, LLLT looks to be a promising and consistent treatment for tendinopathies.

Keywords: CTL; Cyclic tensile tests; DIC; Diclofenac; L1J; L3J; LLLT; Low-level laser therapy; MMP; Matrix metalloproteinases; NSAID; TEN; Tendon mechanical properties; control; low-level laser therapy; matrix metalloproteinase; nonsteroidal anti-inflammatory drug; tendinitis treated by LLLT (1J); tendinitis treated by LLLT (3J); tendinitis treated with diclofenac; untreated tendinitis.