Myofascial pain involving the masticatory muscles: an experimental model

Thirty healthy volunteers were assigned to one of the following two conditions: (1) hyperactivate the lateral pterygoid muscles by vigorously thrusting their mandible forward for 5 min, or (2) a non-exercise control condition. Subjects who protruded their mandible reported significantly more pain than control subjects. This pain was located in the immediate preauricular area. This pain was similar in quality and location to many patients diagnosed as having the myofascial pain-dysfunction syndrome. Other signs or symptoms associated with the syndrome (e.g., tenderness upon palpation, limitation of jaw function) were not produced. This constitutes the first direct, experimental test indicating that the pain of the myofascial pain-dysfunction syndrome may be caused by hyperactivity of the lateral pterygoid muscles.