The medial pterygoid is a thick, quadrilateral muscle forming the medial sling of the temporomandibular joint in concert with the masseter laterally, their combined force creating the pterygoid-masseter sling that suspends the mandibular angle. Its actions of elevation, protrusion, and contralateral jaw deviation mirror those of the masseter but from the medial side of the ramus.
| Origin | Medial surface of the lateral pterygoid plate of the sphenoid; Tuberosity of the maxilla and pyramidal process of the palatine bone |
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| Insertion | Inner surface of the ramus and angle of the mandible, roughly mirroring the masseter on the medial side |
| Nerve Supply | Medial pterygoid nerve (branch of the mandibular nerve, CN V3) |
| Blood Supply | Branches of the maxillary artery |
| Actions | Elevation of the mandible (jaw closing); Protrusion of the mandible; Contralateral jaw deviation (lateral movement) |
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Together with the masseter it forms a muscular sling around the mandibular angle that generates the powerful jaw-closing force needed for molar occlusion, with the two muscles producing a compressive force on the mandibular condyle that stabilises the TMJ.
The medial pterygoid is involved in trismus after inferior alveolar nerve block injections when the needle inadvertently passes through the muscle and causes haematoma. Medial pterygoid tenderness is assessed by intraoral palpation along the inner surface of the mandibular ramus and is a finding in TMJ dysfunction and myofascial pain syndrome. Its position adjacent to the mandibular nerve makes it a site of referred pain from V3 nerve compression.
The medial pterygoid is not accessible through external palpation but is assessed intraorally by placing a gloved finger along the inner surface of the mandibular ramus, where tenderness during jaw clenching indicates medial pterygoid involvement in TMJ dysfunction.
Post-injection or traumatic haematoma within the muscle producing progressive jaw restriction in the days after a dental procedure, managed conservatively with physiotherapy jaw opening exercises as the haematoma resolves.
