Which muscle group is most important for protrusion and influences the articular disc position?

• A. Masseter muscles
• B. Medial pterygoid muscles
• C. Lateral pterygoid muscles (especially the superior head)
• D. Temporalis muscles

Answer: (C)

Protrusion of the jaw is driven mainly by the lateral pterygoid muscles. They attach to the neck of the mandible and to the articular disc, so when they contract they pull the disc–condyle complex forward. The inferior head directly advances the condyle, contributing to forward movement, while the superior head pulls on the articular disc itself via its attachment to the disc and capsule, guiding and stabilizing the disc as the jaw translates forward. Because the superior head acts on the disc, its influence on disc position is especially important during protrusion, helping keep the disc in the correct position relative to the condyle. The other muscles listed primarily support jaw elevation or different movements and don’t regulate protrusion or disc position to the same extent.