Objectives: To analyse the condylar movements of patients with temporo
mandibular disorders and investigate the mutual interaction between bo
th temporomandibular joints (TMJs) by comparing bilateral simultaneous
videofluorography with the disk position on MRI. Methods: Fifty-two p
atients who had been diagnosed as having internal derangement in one o
r both TMJs on the base of the clinical symptoms underwent bilateral s
imultaneous videofluorography and MRI. The TMJs were classified from t
he MRI into three categories: superior disk position (SDP), reducing d
isk displacement (RDD) and nonreducing disk displacement (NDD), Condyl
ar movements of the TMJs were analysed from the videofluorography and
correlated with the MR diagnoses. Results: The range of condylar movem
ent of NDD joints was significantly shorter than that of SDP or RDD jo
ints at maximum mouth opening (P<0.001), but not at maximum protrusion
and lateral protrusion. Based on the sagittal, condylar path during m
aximum mouth opening and closing, three patterns of condylar movement
were identified: normal, deflected and short. Sixty-nine per cent of t
he normal pattern were SDP, 55% of the deflected RDD and 77% of the sh
ort NDD. The condylar movement of a NDD or RDD joint could influence t
he range and pattern of movement of the contralateral joint. Conclusio
ns: Analysis of condylar movement was helpful in assessing the state o
f the disk because they were closely related. The range and pattern of
condylar movement of both TMJs were mutually interrelated. Patients w
ith signs and symptoms of internal derangement should have both sides
examined for an accurate and complete diagnosis.