Frequency TMJ disc displacements.

Background: Temporomandibular joint (TMJ) disorders are characterized by alterations in joint structure and function, with disc displacement being one of the most prevalent pathological findings. The frequency, typology, and clinical correlates of these displacements, particularly with regard to intra-articular effusion, remain insufficiently explored. Material and Methods: The retrospective study included 244 MRI examinations of patients with TMJ disorders. Imaging was performed using standardized protocols on 1.5 T MRI scanners. Disc position was classified according to established radiological criteria. The prevalence and distribution of various disc displacement types, as well as the presence and degree of joint effusion, were systematically evaluated. Results: Anterior disc displacement was identified in 9.84% (right) and 8.61% (left) TMJ of unilateral cases, and in 17.21% (right) and 16.80% (left) TMJ of bilateral cases. Partial anterior disc displacement was observed in 8.61-10.66% of unilateral cases and 15.16-15.57% of bilateral cases. Rotational displacements were found in 6.15-6.56% of unilateral cases and 12.70-13.11% of bilateral cases, while lateral/medial and posterior displacements ranged from 0.41% to 3.69%. A normal disc position was present in 20.90-22.95% of joints. Joint effusion was most often recorded in cases of anterior and partial anterior displacements, predominantly minimal (2.9-5.3%) or small (1.2-2.9%) in degree. In most cases of lateral, posterior, and rotational displacement, as well as with normal disc position, effusion was absent. Conclusions: Anterior disc displacement is the most prevalent TMJ pathology among symptomatic patients, with a frequency up to 17.2% in bilateral cases. Effusion is most closely associated with anterior and partial anterior displacements but is typically minimal or absent. These findings support a predominantly mechanical, rather than inflammatory, etiology for disc displacement in this patient population.