Fig. 1

MRI imaging. A The shape of disc (the arrow indicates the articular disk); B the position of disc (the Angle between the posterior band and the condylar head in the closed-mouth position); C classification of anterior articular disc displacement (depending on the position of the articular disc in the opening position); D joint effusion (the arrow indicates the effusion); E joint motion (the position of the condyle with respect to the articular tubercle in the opening position); F condylar bone morphology (the arrow indicates the bone abnormality). Where: NA = normal; s-ADD = slight to mild anterior disc displacement; m-ADD = moderate to severe anterior disc displacement; PDD = posterior disc displacement; ADDWR = anterior disc displacement with reduction; ADDWoR = anterior disc displacement without reduction