The aim of this study was to evaluate the lateral pterygoid muscle (LPM) area, attachment type, signal intensity and presence of arthrosis, effusion in the temporomandibular joint (TMJ) by magnetic resonance imaging (MRI) according to the position of the articular disc.

The study included a total of 126 TMJs belonging to 69 patients over the age of 18 years who had MRI due to TMJ complaints. The position of the articular disc, the area, attachment type, and signal intensity of the LPM, the presence of arthrosis on the condyle surface, and the presence of effusion in the joint space were evaluated.

The attachment type of the LPM did not show a statistically significant difference according to the position of the articular disc. The groups were not statistically different in terms of LPM intensity. Although the distribution of the LPM area was found to be low in the anterior disc displacement with reduction (R+DD) group and high in the anterior disc displacement without reduction (R-DD) group. It was determined that the rate of arthrosis at the condyle head was significantly higher in the R-DD group compared to the normal disc position group. The incidence of effusion was found significantly higher in the R-DD and R+DD groups than joints with normal disc position.

Pathological changes in LPM and TMJ can be detected by MRI. In the group with R-DD, the rate of arthrosis at the condyle head, effusion, LPM area, and intensity of the Sup. LPM were higher.