OBJECTIVES: This study aimed to establish a reproducible and minimally invasive rat model of temporomandibular joint osteoarthritis (TMJ-OA) using intra-articular monoiodoacetic acid (MIA) injection, and to investigate the pathological mechanisms underlying TMJ-OA development, aimed at providing insights for potential clinical treatments. DESIGN: We compared the effects of single versus multiple MIA injections on body weight, pain behaviour, and condylar pathology in female Sprague-Dawley rats. We longitudinally assessed the progression of TMJ-OA over 5 weeks by evaluating condylar pathology and immunohistochemical staining. We investigated the potential mechanism of MIA-induced TMJ-OA through transcriptome sequencing and polymerase chain reaction validation. RESULTS: A single MIA injection (0.5 mg) into the joint space effectively induced TMJ-OA in rats and sustained inflammatory reactions and pain without significantly affecting weight. MIA continuously promoted the development of TMJ-OA through the activation of the toll-like receptor pathway, oestrogen metabolism promotion, oxidative stress response enhancement, and energy metabolism alteration in condylar chondrocytes. CONCLUSION: We have presented a simple and minimally invasive method for modelling TMJ-OA in rats, which can be utilised in animal trials focusing on TMJ-OA treatment strategies. The study also reveals toll-like receptor, oestrogen, oxidative stress, and altered energy metabolism as key drivers of TMJ-OA in female rats.