Aims: Arthrogryposis multiplex congenita (AMC) is characterized by congenital contractures and joint deformities, but there are only a few reports of temporomandibular joint (TMJ) involvement. The objective of this investigation was to study the cause of limited mouth movement in this disease. Materials and Methods: Four individuals from a family affected by AMC over 5 generations were examined clinically and by magnetic resonance imaging (MRI) and 3-dimensional computerized tomography (3D-CT). Results: The CT scans of the 4 individuals showed hyperplasia of the coronoid process protruding into the infratemporal fossa in 2 of them and cranially to the zygomatic arch in the other 2; the hyperplasia was associated with mechanical limitation of the mouth opening. The MRI showed a disc displacement with reduction in 1 patient and a disc displacement without reduction in another; disc displacement could not be evaluated because of the limited mouth opening in the other 2. The condyle-disc complex of these last 2 individuals could only rotate. The MRI on T2-weighted images showed disc hyposignal in all cases but no alterations in the masticatory muscle tissue. The pedigree of the family suggests an autosomal dominant form of inheritance. Conclusions: The restriction of mouth opening in the 4 individuals affected by AMC was likely due to osseous dysplasia. J Orofac Pain 2005;19:82–88