Background: This study investigated the factors involving joint effusion in patients with temporomandibular disorders. Methods: The magnetic resonance images of 131 temporomandibular joints (TMJs) of patients with temporomandibular disorders were evaluated. Gender, age, disease classification, duration of manifestation, muscle pain, TMJ pain, jaw opening disturbance, disc displacement with and without reduction, deformation of the articular disc, deformation of bone, and joint effusion were investigated. Differences in the appearance of symptoms and observations were evaluated using cross-tabulation. The differences in the amounts of synovial fluid in joint effusion vs. duration of manifestation were analyzed using the Kruskal–Wallis test. Multiple logistic regression analysis was performed to analyze the factors contributing to joint effusion. Results: Manifestation duration was significantly longer when joint effusion was not recognized (p < 0.05). Arthralgia and deformation of the articular disc were related to a high risk of joint effusion (p < 0.05). Conclusions: The results of this study suggest that joint effusion recognized in magnetic resonance imaging was easily observed when the manifestation duration was short, and arthralgia and deformation of the articular disc were related to a higher risk of joint effusion.

In this study, we investigated joint effusion in patients with temporomandibular disorders (TMDs) with disc displacement. The magnetic resonance (MR) images of 97 temporomandibular joints (TMJs) were evaluated, and the appearance of joint effusion was investigated. Myofascial pain and TMJ pain were considered in addition to the duration from manifestation. Disc displacement with and without reduction, as well as the region and the area of joint effusion, were investigated using the MR images. Fisher’s test was used for the analyses. Joint effusion was recognized in 70 TMJs, including 55 in the superior articular cavity, 1 in the inferior articular cavity, and 14 in both the superior and inferior articular cavities. The appearance of joint effusion did not differ with the existence of myofascial pain or TMJ pain. The region of joint effusion did not differ between disc displacement with and without reduction. A larger area of joint effusion was recognized in disc displacement without reduction (p < 0.05). The results showed that the amount of synovial fluid in the joint effusion did not change with the existence of myofascial pain or TMJ pain. Joint effusion commonly appeared in disc displacement without reduction.

We aimed to investigate the type of bone changes in temporomandibular disorder patients with disc displacement. The subjects were 117 temporomandibular joints that were diagnosed with anterior disc displacement using magnetic resonance imaging (MRI). Temporomandibular joint (TMJ) pain and opening dysfunction were examined. Disc displacement with and without reduction, joint effusion, and bone changes in the mandibular condyle were assessed on MRI. The types of bone changes were classified into erosion, flattening, osteophyte, and atrophy on the MR images. Fisher’s exact test and χ² test were performed for analyses. Bone changes were found on 30.8% of subjects with erosion, flattening, osteophyte, and atrophy types (p < 0.001). The occurrence of joint effusion appearance (p < 0.001), TMJ pain (p = 0.027), and opening dysfunction (p = 0.002) differed among the types of bone changes. Gender differences were also found among the types of bone changes (p < 0.001). The rate of disc displacement with reduction was significantly smaller than that of disc displacement without reduction on flattening and osteophyte (p < 0.001). The results made it clear that the symptoms, gender, and presence or absence of disc reduction differed among the types of bone changes.