The medial pterygoid forms the inner limb of the mandibular sling (with the masseter on the outer limb), suspending the mandibular angle between them. Its action in jaw closing and protrusion complements the masseter. Medial pterygoid trismus after inferior alveolar nerve block or mandibular third molar surgery results from haematoma or direct muscle trauma during needle insertion.
| Origin | Deep head: medial surface of the lateral pterygoid plate and pterygoid fossa. Superficial head: maxillary tuberosity and pyramidal process of the palatine bone |
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| Insertion | Medial surface of the mandibular ramus and angle — forming the medial pterygoid plate sling with the masseter |
| Nerve Supply | Medial pterygoid nerve (mandibular nerve V3) |
| Blood Supply | Pterygoid branches of the maxillary artery |
| Actions | Mandibular elevation (jaw closing); Jaw protrusion; Contralateral jaw movement (lateral excursion opposite side) — chewing motion |
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Post-injection trismus from medial pterygoid haematoma or spasm resolves with jaw exercises, heat, and NSAIDs over 2-4 weeks. Persistent trismus warrants MRI to exclude submasseteric abscess. In mandibular condyle fractures, the medial pterygoid muscle displaces the proximal segment medially and superiorly — ORIF must overcome this muscular displacement force.
The medial pterygoid is not palpable from the surface but is assessed by intraoral palpation at the posterior medial mandible during jaw movements.
Post-injection or post-surgical medial pterygoid spasm producing restricted mouth opening managed with physiotherapy, NSAIDs, and heat.
