The lateral pterygoid is the only masticatory muscle that actively opens the jaw, working with the suprahyoid muscles to depress the mandible. Its superior head's direct attachment to the articular disc and joint capsule of the TMJ makes it unique as the only muscle that directly controls the disc position during condylar translation. Dysfunction of the superior head disc attachment is central to the pathology of internal TMJ derangement.
| Origin | Infratemporal surface and crest of the greater wing of the sphenoid; Lateral surface of the lateral pterygoid plate of the sphenoid |
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| Insertion | Articular disc and capsule of the temporomandibular joint; Pterygoid fovea on the neck of the mandibular condyle |
| Nerve Supply | Lateral pterygoid nerve (branch of the mandibular nerve, CN V3) |
| Blood Supply | Branches of the maxillary artery |
| Actions | Protrusion of the mandible (both heads acting together); Depression of the mandible (inferior head, with suprahyoid muscles); Lateral jaw deviation to the opposite side; Guides condylar translation during jaw opening (superior head controls disc movement) |
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During mouth opening the inferior head protrudes and depresses the condyle while the superior head controls the forward translation of the articular disc ahead of the condyle, preventing the disc from being left behind as the condyle slides forward.
Lateral pterygoid hyperactivity and spasm is a major contributor to TMJ internal derangement and disc displacement without reduction, producing the characteristic limited jaw opening with contralateral deviation. Botulinum toxin injection into the lateral pterygoid under EMG guidance is used for refractory TMJ myofascial pain. The muscle is in close proximity to the pterygoid venous plexus and haemorrhage from its disruption during dental procedures can cause retropharyngeal haematoma.
The lateral pterygoid is not accessible to direct palpation due to its deep position in the infratemporal fossa. It is assessed indirectly by provocation testing with resisted contralateral jaw deviation and protrusion.
Muscle hyperactivity producing jaw deviation toward the affected side, clicking, and limited opening that is part of the TMJ internal derangement spectrum, managed with splint therapy and lateral pterygoid injection in refractory cases.
