The medial pterygoid is one of the four main muscles responsible for mastication (chewing). This short, thick, quadrilateral muscle is located deep within the skull, making it difficult to access and often overlooked when discussing jaw pain. It plays a significant role in overall jaw health and movement mechanics.
Where the Medial Pterygoid Is Located
The medial pterygoid muscle is situated in the infratemporal fossa, a deep region of the skull behind the cheekbone and beneath the temporal bone. It is an internal muscle that runs vertically, tucked between the lateral pterygoid muscle and the inner surface of the lower jawbone.
The muscle originates via two distinct heads, a deep and a superficial one, primarily from the medial side of the lateral pterygoid plate of the sphenoid bone. Its fibers pass downward, backward, and laterally toward the lower jaw. It inserts into a roughened area on the inner surface of the ramus and angle of the mandible (the back, upright portion and corner of the lower jawbone). This attachment point is high up, reaching near the mandibular foramen. Along with the masseter muscle, the medial pterygoid creates a muscular sling that suspends the mandible, contributing to its stability and strength.
The Mechanics of Jaw Movement
The medial pterygoid muscle has three main functions. Its primary action is the elevation of the mandible, which closes the jaw. When contracting with the temporalis and masseter muscles, the medial pterygoid provides the force needed to bite down firmly.
The muscle also contributes to the protrusion of the jaw, the motion of jutting the lower jaw forward. This action occurs when both the left and right medial pterygoid muscles contract simultaneously, working with the lateral pterygoid muscles.
The third movement the medial pterygoid facilitates is lateral excursion, the side-to-side movement of the jaw. Lateral movement is achieved through the unilateral contraction of the muscle, meaning the medial pterygoid on one side works to swing the jaw toward the opposite side.
Symptoms of Medial Pterygoid Dysfunction
When the medial pterygoid muscle becomes strained, tight, or develops trigger points, it can lead to uncomfortable and confusing symptoms. Because of its deep, internal location, pain is frequently perceived in other nearby areas, leading to misdiagnosis. Pain may be felt deep within the ear, sometimes mimicking an ear infection, or just below and behind the temporomandibular joint (TMJ).
A common sign of dysfunction is difficulty fully opening the mouth, known as trismus or “lockjaw.” This restriction occurs because a tight medial pterygoid physically limits the range of motion of the mandible. Individuals may also experience discomfort or pain when swallowing, yawning, or talking for extended periods.
Trigger points in this muscle can refer pain to the back of the mouth, the throat, and the hard palate. Dysfunction often contributes to Temporomandibular Joint Disorder (TMD), a condition marked by jaw pain and restricted movement. The pain is often described as a deep ache that is exacerbated by chewing tough foods or by habits like teeth clenching or grinding.