What is associated with joint effusion in the temporomandibular joint, disc displacement, or degenerative bone changes? : a radiological study

We aimed to investigate associations between joint effusion (JE) and age, sex, disc displacement, and degenerative condylar changes in the temporomandibular joints (TMJ) through multivariate analysis of a large MRI dataset and to determine its clinical significance. This retrospective study analysed MRI data from 761 outpatients (1,522 TMJs; average age: 45.8 ± 18.2 years; 582 women, 179 men) with temporomandibular disorder symptoms who underwent MRI examination. Degenerative condylar changes were assessed, and JE was classified into five categories: none, trivial, mild, moderate, and severe. Ordinal logistic regression, accounting for mixed effects, identified associations between JE and predictors (age, sex, disc displacement, and degenerative bone changes: concavity, atrophy, erosion, flattening, osteophytes, and subchondral cysts). Two examiners independently evaluated MRI images, resolving discrepancies through forced consensus. Forced consensus was required for 8.5% (129/1,522) of TMJs. JE classifications of none, trivial, mild, moderate, and severe were observed in 45%, 11.8%, 21%, 14.1%, and 7.7% of TMJs, respectively. Ordinal logistic regression revealed significant associations between JE and age, erosion, osteophytes, and concavity. JE occurrence decreased with age, with erosion showing the strongest association. Disc displacement was not significantly associated with JE. Within the limitations of this study, JE was significantly associated with degenerative condylar changes rather than disc abnormalities, suggesting its potential as an imaging marker of progressive bone changes. Future large-scale longitudinal investigations are essential to confirm the causal pathways between JE and degenerative condylar changes.