Low Intensity Pulsed Ultrasound Alleviates the Pain of Monosodium Iodoacetate‐Induced Osteoarthritis in Rats

OBJECTIVES: Osteoarthritis pain is a common chronic pain. Low intensity pulsed ultrasound (LIPUS) is a non-invasive treatment commonly used for musculoskeletal system diseases, but it is unclear whether it can alleviate osteoarthritis (OA) pain. The aim of this study is to investigate the therapeutic effects of LIPUS on pain relief and joint repair in OA rat models, and to explore its potential mechanisms. METHODS: Twenty-four Sprague-Dawley rats were divided into Sham, monosodium iodoacetate (MIA), MIA + LIPUS, and MIA + Sham LIPUS groups. OA was induced via intra-articular MIA injection. LIPUS was administered for 20 minutes/14 days. Behavioral tests, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), histopathological, and immunohistochemical assessments were conducted. RESULTS: LIPUS significantly increased paw withdrawal thresholds (PWT) and thermal withdrawal latencies (PWL), improved gait symmetry, and enhanced total walking distance. Piezo1, Piezo2, Trpv1, and Calca (encoding CGRP) mRNA levels in dorsal root ganglia were downregulated. Histopathological and immunohistochemical analysis revealed that LIPUS treatment preserved cartilage matrix integrity, reduced cartilage surface erosion, decreased Mankin scores, and promoted cartilage regeneration. CONCLUSION: LIPUS significantly alleviated OA-induced pain and joint damage in rats by downregulating mRNA expression of pain-related molecules and promoting cartilage preservation. These findings suggested that LIPUS has the potential to be a non-invasive, non-pharmacological therapy for OA, offering a promising alternative to conventional treatments.