The lateral pterygoid muscle plays an important role in prober jaw function. It originates on the greater wing of the sphenoid bone and the lateral pterygoid plate, and inserts on the condyloid process of the mandible. It’s action is to pull the head of the mandibular condyle out of the mandibular fossa while opening the jaw. When trigger points develop they refer pain into the temporal mandibular joint and maxillary sinus. This referral is commonly mistaken for TM arthritis. In addition to the referral pain, trigger points in this muscle can also effect proper movement of the jaw.