The pterygoid muscles are a pair of deep jaw muscles, the medial pterygoid and the lateral pterygoid, that sit behind your upper jaw on each side of the skull. They are buried so deep that you cannot see or feel them the way you can feel your temples flex when you clench, yet they are central players in chewing, jaw opening, and side-to-side grinding. Because of their hidden location and complex anatomy, the pterygoid muscles are also frequent troublemakers in jaw pain, clicking, and temporomandibular joint (TMJ) problems.
Where the Pterygoid Muscles Are and What They Look Like
Both muscles live in a narrow space called the infratemporal fossa, roughly behind the cheekbone and below the base of the skull. The medial pterygoid runs from the pterygoid plates of the sphenoid bone (bony wings deep inside the skull) down to the inner surface of the lower jaw near its angle. The lateral pterygoid is positioned higher and more horizontally, connecting the skull base to the jaw joint and the neck of the jawbone’s condyle (the knob that fits into the joint socket).
Despite sharing a name, the two muscles differ in shape, fiber direction, and job. The medial pterygoid is thick and roughly rectangular, making it a mirror image of the masseter muscle on the outside of the jaw. Together, the medial pterygoid on the inside and the masseter on the outside form a muscular sling that cradles the angle of the jaw. Detailed dissection has shown that the medial pterygoid has a penniform (feather-like) internal architecture made up of seven alternating layers of muscle and tendon, giving it greater force output per unit of size than a simpler parallel-fiber muscle would have.1PubMed. Anatomical study of the arrangement and attachments of the human medial pterygoid muscle Its fibers are relatively short, averaging around 12 to 14 millimeters, but its cross-sectional area is large, which is a design suited for powerful biting rather than wide-range movement.2PubMed. Architecture of the human pterygoid muscles
The lateral pterygoid is shaped differently. It fans out roughly horizontally, and most descriptions divide it into two distinct heads: a superior (upper) head and an inferior (lower) head. The inferior head is larger and originates from the outer surface of the lateral pterygoid plate, while the superior head starts higher, from the roof of the infratemporal fossa. The two heads converge toward the jaw joint, but they do not always land on the same target. A cadaver study found three patterns of where the superior head attaches: in about 56% of specimens it inserted into both the condyle and the joint disc, in roughly 28% it went only into the condyle, and in about 17% it attached purely to the disc-capsule complex.3PubMed. Variations of the attachment of the superior head of human lateral pterygoid muscle That variability matters clinically because the disc connection is one pathway through which muscle dysfunction can pull the joint disc out of position.
Anatomy That Textbooks Often Get Wrong
Standard anatomy textbooks tend to describe the medial pterygoid’s origin as a fairly tidy attachment to the medial surface of the lateral pterygoid plate. A dissection study of 35 specimens found that description held in fewer than a third of cases. In about 72% of specimens the origin was wider than conventionally described, extending onto the lateral surface of the neighboring medial pterygoid plate as well.4PubMed. The human medial pterygoid muscle: Attachments and distribution of muscle spindles This wider footprint means the muscle grabs more real estate on the skull base than most diagrams suggest, which can change how surgeons plan approaches through this region.
The lateral pterygoid is similarly underrepresented by simple diagrams. Embryological work tracking human specimens from five to fourteen weeks of fetal development found that by week fourteen the lateral pterygoid already had several internal tendon sheets dividing it into three functional parts, not the neat two-headed layout most students learn.5PubMed. The embryologic development of the human lateral pterygoid muscle and its relationships with the temporomandibular joint disc and Meckel’s cartilage The blood supply running through the area is also variable. The maxillary artery, the main vessel of the deep face, sometimes threads through or around the lateral pterygoid in unusual ways, occasionally splitting into branches that pass both superficial and deep to the muscle belly.6PubMed Central. Divided maxillary artery in relation to the lateral pterygoid muscle Surgeons and dentists need to keep these vascular variations in mind during procedures anywhere near this space.
What the Pterygoid Muscles Actually Do
The medial pterygoid is primarily a jaw-closing muscle. Along with the masseter and temporalis, it pulls the lower jaw upward when you bite down. Electromyography (EMG) studies show that both left and right medial pterygoids activate early in the closing phase of each chewing cycle, but the muscle on the chewing side fires more strongly during the crushing phase when the teeth meet.7PubMed. Medial pterygoid muscle activity during the closing and compressive phases of human mastication It also plays a limited role in swinging the jaw sideways in the opposite direction, working together with the lateral pterygoid on the same side.8IntechOpen. Biomechanics of the Temporomandibular Joint One interesting finding from EMG work is that the medial pterygoid can stay quiet during a simple open-close clenching task even while the masseter is contracting vigorously. It seems to be recruited most during the complex grinding motions of real chewing, not during static bite force.9PubMed. Medial pterygoid muscle activity during the closing and compressive phases of human mastication
The lateral pterygoid is the more functionally unusual of the two. Its inferior head is a classic jaw-opening helper: it contracts to pull the condyle forward and downward as you open wide, and it drives protrusion (pushing the lower jaw forward). But the superior head does nearly the opposite. EMG recordings show the superior head behaves like a jaw-closing muscle. It maintains background activity even when the jaw is at rest in the bite-together position and ramps up during clenching, reaching near-maximum effort at relatively low bite forces. Stretch reflexes detected in the superior head suggest it acts as a stabilizer, keeping the condyle pressed forward against the socket during biting so the bite force does not pull the condyle backward.10PubMed. EMG activities of two heads of the human lateral pterygoid muscle in relation to mandibular condyle movement and biting force
Biomechanical modeling confirms this division of labor. As the jaw opens, there is a clear switching point at which activity flips from the superior head to the inferior head.11Archives of Oral Biology. Biomechanical implications of lateral pterygoid contribution to biting and jaw opening in humans Needle EMG studies likewise found the inferior head was silent or barely active during clenching and ipsilateral side movements, but fired strongly and bilaterally during jaw opening, protrusion, and swallowing.12PubMed Central. Anatomical and electromyographic studies of the lateral pterygoid muscle Overall jaw-closing simulations show the medial pterygoid and different parts of the masseter are the muscles best suited for producing the combined sliding and rotating movement of the condyle that happens during a normal bite.13PubMed. Biomechanical analysis of jaw-closing movements
Pterygoid Muscles and TMJ Disorders
The lateral pterygoid’s direct connection to the joint disc makes it a key suspect in TMJ disc displacement, the condition behind many cases of jaw clicking, locking, and pain. When the superior head goes into spasm, it can pull the disc forward out of its normal position on top of the condyle.14PubMed Central. Pathologic changes of the lateral pterygoid muscle in patients with derangement of the temporomandibular joint disk: objective measures at MR imaging MRI studies in patients with disc displacement have found a recognizable sequence: the muscle spasms first, which displaces the disc, and then the muscle itself begins to atrophy and degenerate as a consequence of the displacement it caused.15PubMed. A possible etiology of the internal derangement of the temporomandibular joint based on the MRI observations of the lateral pterygoid muscle This creates a feedback loop: dysfunction breeds structural change, which breeds more dysfunction.
Trigger points in the lateral pterygoid can also refer pain to the TMJ itself and to the area around the maxillary sinus, which is why people with pterygoid muscle problems sometimes feel deep facial pain that mimics sinus trouble.16PubMed Central. Deep dry needling of trigger points located in the lateral pterygoid muscle: Efficacy and safety of treatment for management of myofascial pain and temporomandibular dysfunction Even more unexpectedly, lateral pterygoid dysfunction has been linked to a specific type of tinnitus: sudden brief episodes of ringing in one ear that fade over a few seconds. Research found these episodes were associated with the lateral pterygoid on the same side, and dry needling the muscle eliminated them.17Otology & Neurotology. Sudden Brief Unilateral Tapering Tinnitus (SBUTT) Is Closely Related to the Lateral Pterygoid Muscle That connection surprises most people, because ear symptoms are not where you would expect a jaw muscle to show up.
Seeing the Muscles on Imaging
Because the pterygoid muscles are hidden behind bone, clinical assessment relies heavily on MRI. Standard MRI can identify hypertrophy (overgrowth), atrophy (wasting), fatty infiltration, and contracture in these muscles.18PubMed. MR imaging of muscles of mastication One MRI study focused on the lateral pterygoid found hypertrophy in about 1.5% of examined muscles and atrophy or contracture in roughly 3% each.19PubMed Central. Evaluation of the lateral pterygoid muscle using magnetic resonance imaging Those numbers are from routine scans, not from a TMJ-disorder population, so the rates would be higher in people with symptoms.
Systemic muscle diseases can also show up here. In patients with myotonic dystrophy, MRI revealed masticatory muscle involvement in roughly 87% of cases, with the hallmark changes being fatty infiltration and volume loss.20PubMed. Temporomandibular joint and masticatory muscle involvement in myotonic dystrophy: a study by magnetic resonance imaging Because the pterygoid muscles are rarely examined in isolation during a general medical workup, disease in these muscles can go undetected unless a clinician specifically looks for it.
Treatments That Target the Pterygoid Muscles
For chronic TMJ-related pain or clicking thought to originate in the lateral pterygoid, two interventional approaches have gained attention: dry needling and botulinum toxin (Botox) injections. Dry needling inserts a thin needle directly into a trigger point to release it. Because the lateral pterygoid sits deep behind the upper jaw, the needle is typically guided through the mouth, aiming behind the last upper molar and angling upward and inward. The procedure is uncomfortable, but studies report improvement in referred facial pain and even resolution of associated tinnitus.21PubMed Central. Deep dry needling of trigger points located in the lateral pterygoid muscle: Efficacy and safety of treatment for management of myofascial pain and temporomandibular dysfunction
Botox injections work by temporarily weakening the muscle, reducing spasm. In a randomized trial comparing Botox to placebo injected into the lateral pterygoid, clicking severity did not significantly improve, but pain scores and functional indices did drop more in the Botox group, and lateral jaw movements improved significantly.22PubMed Central. The effects of botulinum toxin A injection on the lateral pterygoid muscle in patients with a painful temporomandibular joint click For chronic jaw dislocation, where the condyle slips completely out of the socket and gets stuck, ultrasound-guided Botox injection into the lateral pterygoid has shown promise. A case series of patients with involuntary dislocation found the treatment successfully controlled the problem without significant complications.23PubMed Central. Ultrasound-guided intraoral botulinum toxin injection into the lateral pterygoid muscle for chronic temporomandibular joint dislocation
Neither treatment is a permanent fix in every case. Botox wears off in a few months, and dry needling may need to be repeated. Conservative treatments like physical therapy, bite splints, and stress management remain first-line for most TMJ problems, with these interventional options reserved for cases that do not respond.
Risks of Procedures Near the Pterygoid Muscles
The infratemporal fossa is a crowded neighborhood. The maxillary artery, a network of veins called the pterygoid venous plexus, and multiple cranial nerve branches all run alongside or through the pterygoid muscles. This makes any needle or instrument that passes through the area potentially hazardous. One of the most common dental nerve-block procedures, the posterior superior alveolar nerve block, targets a nerve that runs right next to the pterygoid muscles. If the needle nicks the pterygoid venous plexus or the maxillary artery, a hematoma can form rapidly in the infratemporal fossa. In roughly 3% of these blocks, accidental blood vessel puncture occurs, sometimes causing dramatic swelling, bruising, or even transient visual disturbances like blurred vision or brief blindness when blood tracks into the orbit.24PubMed Central. Edema and hematoma after local anesthesia via posterior superior alveolar nerve block: a case report The posterior superior alveolar nerve block carries the highest hematoma risk among common dental blocks.25Journal of Dental Problems and Solutions. Hematoma – A Complication of Posterior Superior Alveolar Nerve Block
Skull-base surgeons also encounter the pterygoid muscles when accessing deep tumors or vascular lesions. Endoscopic routes that go through the back wall of the maxillary sinus and into the space behind it must navigate around these muscles and the structures threaded through them. Cadaver-based surgical training studies describe these approaches as opening corridors to the middle cranial fossa, the cavernous sinus, and the internal carotid artery, all of which lie just beyond the pterygoid muscles.26PubMed Central. Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees The pterygoid muscles essentially act as a muscular gateway that surgeons must either retract or work around to reach these deeper targets.
How the Pterygoid Muscles Evolved
The pterygoid muscles have a deep evolutionary history tied to one of the most dramatic transitions in vertebrate anatomy: the shift from a reptile-style jaw joint to the mammalian jaw joint. In reptiles and early mammal ancestors, the jaw joint was formed by two small bones (the articular and the quadrate) that eventually shrank and migrated into the middle ear to become the malleus and incus, two of the tiny hearing bones. As that transition happened, the jaw muscles had to reorganize their attachments to the changing jawbone.
Current evidence suggests the modern mammalian arrangement of jaw muscles, including a pterygoid group inserting on the dentary (the single mammalian jawbone), was complete before the fully mammalian jaw joint itself finished evolving. Muscle reconstructions of early mammal relatives from around 200 million years ago already show a pterygoid muscle attaching to the dentary bone in roughly the modern pattern.27PubMed Central. Morphological evolution of the mammalian jaw adductor complex Recent fossil work proposes that the pterygoid muscle’s insertion migrated from the old articular bone to a ridge on the inner surface of the dentary as the jaw joint shifted, and that modern egg-laying mammals (monotremes like the platypus) may preserve the ancestral mammalian configuration.28bioRxiv. Reexamining the evolutionary history of the mammalian medial pterygoid muscle In other words, the pterygoid muscles helped stabilize the jaw during one of evolution’s most complex anatomical remodeling projects, and the muscle arrangement you have today was essentially locked in before mammals as a group fully existed.
When Pterygoid Problems Mimic Other Conditions
One practical challenge with pterygoid-related pain is that it rarely announces itself as a muscle problem. The deep location of these muscles means the pain they produce tends to be felt somewhere else. Lateral pterygoid trigger points commonly refer pain to the jaw joint, the cheek, and the area around or behind the eye. Medial pterygoid problems can cause pain deep in the ear, at the back of the mouth, and into the throat, sometimes making swallowing feel uncomfortable. Patients may see an ENT specialist for ear pain, an allergist for what feels like chronic sinus pressure, or a dentist suspecting a cracked tooth before anyone considers the pterygoid muscles.
There is no simple self-test for pterygoid dysfunction. The muscles are too deep to palpate externally in any reliable way, though a clinician can press on the medial pterygoid through the mouth along the inner surface of the jaw angle, and reach the lateral pterygoid by pressing behind the last upper molar and directing pressure upward. Tenderness during these maneuvers, combined with symptoms that match the referral patterns, is a strong clue. MRI can confirm structural changes if needed, but in many cases the diagnosis is clinical, based on the story the patient tells and what reproduces the pain on examination.