Effect of Low-Intensity Pulsed Ultrasound on Post-Traumatic Intra-Articular Knee Adhesions in Rats.

Abstract

Objective: Intra-articular adhesions (IAA) caused by trauma or surgical invasion commonly elicit pain and motor dysfunction. However, effective treatments for preventing IAA remain elusive. This study investigated the effects of low-intensity pulsed ultrasound (LIPUS) therapy on IAA after immobilization following trauma.

Methods: A knee adhesion model was established in male Wistar rats, which were divided into LIPUS and sham groups. LIPUS was applied for 20 min/d (30 mW/cm² [spatial average temporal average], 1 MHz, duty cycle 20%, 5 times/wk, for 1, 2 and 3 wk). Another group of rats was treated with the same parameters for 3 or 7 d. After the treatment period, we evaluated the range of motion (ROM) of the knee joint, the length of the adhesion and the posterior knee joint capsule. RNA-seq and RT-quantitative polymerase chain reaction were performed to investigate the molecular mechanisms underlying the effects of LIPUS.

Results: The knee ROM was significantly improved, and the adhesion length was reduced in the LIPUS group. RNA-seq identified 113 and 776 differentially expressed genes on days 3 and 7, respectively, highlighting pathways related to inflammatory, immune and fibrotic responses. IL-6 mRNA in the LIPUS group was significantly upregulated on day 3 and significantly downregulated at 1 wk. The TNFα, TGFβ and HIF1α levels did not differ between all groups. COL1A1 expression in the sham group significantly increased on day 7.

Conclusion: These results indicate that LIPUS therapy may affect inflammatory and fibrotic pathways and may serve as a rehabilitation approach to prevent the development of IAA.