Temporomandibular disorders can usually be diagnosed on the basis of a thorough history and a comprehensive examination of the patient. Additional diagnostic tests, such as imaging of the temporomandibular joint (TMJ) area, are mandatory and must be flawless in case of atypical findings. The aim of this report is to illustrate pitfalls in clinical reasoning and in imaging procedures in the diagnosis of temporomandibular pain and dysfunction. A case report of a patient with osteocartilaginous exostosis of the mandibular condyle, which was erroneously diagnosed and treated as an internal derangement of the TMJ for half a year, is presented.