TMJ Intra-articular Disorders: Impact on Pain and Jaw Function

Objective: To assess the association of TMJ intra-articular disorders with jaw pain and functional limitations. Methods: This cross-sectional case-control study consisted of the 705 participants (614 temporomandibular disorders (TMD) cases and 91 controls) from the multi-center Validation Project. All subjects had bilateral temporomandibular joint (TMJ) magnetic resonance imaging and computed tomography. Subjects had a TMD expert-based consensus diagnosis of normal TMJs, disc displacement with reduction (DDwR), DD without reduction (DDw/oR) or degenerative joint disease (DJD). Subjects were divided into these four groups based on their most advanced diagnosis present in either TMJ. Characteristic Pain Intensity (CPI) and jaw functional limitations, derived from the Jaw Functional Limitation Scale (JFLS), were calculated for each subject. Differences in CPI or JFLS scores among the 4 diagnostic groups were analyzed using Analysis of Variance. Results: For CPI scores, significant differences (p-value < 0.001) were found among the four groups for pain intensity during the prior month. The lowest mean CPI was observed for subjects with normal joints (21/100) and highest for DJD (44/100). When group differences were expressed as effect sizes, a “large” effect size was observed for CPI scores for the prior month (Cohen's d = 0.88). For JFLS scores, significant differences (p-value < 0.001) were found for the global score. Subjects with DDw/oR and DJD had higher JFLS scores (35 and 32 units, respectively) than subjects with normal TMJs (14 units) or subjects with DDwR (19 units). A large effect size for functional limitations was observed (d = 0.81). Conclusions: Contrary to common belief, the presence of advanced TMJ intra-articular disorders (DDw/oR and/or DJD) is significantly associated with patient-reported outcomes of pain intensity and jaw functional limitations. The contribution of intra-articular disorders should be considered when evaluating the biological component of the biopsychosocial model for TMD. Funded by NIDCR U01 DEO13331.