Muscle:Lateral Pterygoid
Lateral pterygoid (external pterygoid) is the primary myofascial source of referred pain felt in the TMJ area. Its TrPs are easily mistaken for TMJ arthritis, and the diagnosis is frequently missed because treatment is misdirected to the joint and teeth. The muscle has two divisions — superior and inferior — with somewhat different functions and clinical presentations.
Anatomy
The lateral pterygoid has two distinct heads:
- Superior division — arises from the infratemporal surface of the greater wing of the sphenoid; inserts into the articular disc and capsule of the TMJ
- Inferior division — arises from the lateral surface of the lateral pterygoid plate; inserts into the pterygoid fovea of the condylar neck
Primary actions: The inferior division depresses and protrudes the mandible (jaw opening and forward movement); the superior division controls the articular disc during closing. Together they produce contralateral excursion of the mandible.
Innervation: Lateral pterygoid nerve, a branch of the anterior division of the mandibular nerve (V3).
Referred Pain Patterns
TrPs in the lateral pterygoid refer pain:
- Deep into the TMJ
- To the region of the maxillary sinus — severe pain here with autonomic concomitant of excessive secretion may be misdiagnosed as sinusitis ("sinus attack")
- Pain is not referred to the teeth — this distinguishes lateral pterygoid from masseter and temporalis
The lateral pterygoid is the chief myofascial source of referred pain felt in the TMJ area. Severe pain in the TMJ region is commonly referred from TrPs in the lateral pterygoid, medial pterygoid, or deep layer of the masseter. This TrP pain referred to the TMJ, along with altered occlusion due to TrP tension and muscle shortening, has frequently caused treatment to be misdirected to the joint and teeth with frustrating results.
Tinnitus
Patients experiencing tinnitus may have lateral pterygoid TrPs responsible for it.
TMJ Clicking
Clicking sounds in the TMJ area may result from dysfunction of the lateral pterygoid muscles.
Activation and Perpetuating Factors
- Bruxism — may be either a cause or a result of lateral pterygoid TrPs; contributes strongly to overuse
- Nail biting
- Excessive gum chewing
- Persistent thumb sucking in childhood
- Playing a wind instrument with the mandible fixed in protrusion
- Violin playing with mandibular pressure
- Satellite TrP activation from neck muscles — especially SCM — which may in turn be activated by lower limb length inequality, small hemipelvis, or other lower body postural abnormality
- Suboptimal levels of vitamins B1, B6, B12, or folic acid — may act as systemic perpetuating factors through increased central nervous system and neuromuscular irritability, aggravating bruxism
- Forward head posture and poor tongue posture
Clinical Examination
Mandibular Range of Motion
When the inferior division is affected:
- Slight decrease in jaw aperture — may prevent entry of two knuckles between incisor teeth
- Lateral excursion of the mandible is reduced toward the same side as the involved muscle due to increased muscle tension
- When the patient slowly opens and closes the jaws, the midline incisal path wobbles from side to side — the most marked deviation during movement is usually away from the side of the more affected lateral pterygoid, but this is not a reliable sign as other masticatory muscles can alter it
Tongue Position Test — Lateral Pterygoid Isolation
This is a key clinical test for isolating lateral pterygoid dysfunction:
- Ask the patient to slide the tip of the tongue backward along the roof of the mouth to the posterior border of the hard palate
- This eliminates lateral pterygoid function by strongly inhibiting translation of the condyles across the articular tubercle
- With the mouth opened in this way, observe the incisal path:
| Finding | Interpretation |
|---|---|
| Incisal path straightens out | Lateral pterygoid dysfunction is the chief cause of the muscular imbalance |
| Incisal path still zigzags | Other muscles and/or TMJ derangement responsible — may or may not also involve lateral pterygoid |
Condylar Displacement and Occlusal Test
Shortening of the inferior division displaces the mandibular condyle anteriorly, causing:
- Premature contact of anterior teeth on the opposite side
- Altered occlusion of posterior teeth on the same side
- Little pain in this displaced resting position
- Closing the teeth fully induces pain referred to the TMJ on the same side as the involved muscle
- Vigorous closure increases the pain
Tongue blade test: Insert a tongue blade between the molar teeth on the painful side. If this eliminates the pain on vigorous clenching, this strongly implicates the inferior division of the lateral pterygoid on the painful side.
Resisted Protrusion Test
A simpler but less sensitive test — ask the patient to protrude the jaw against resistance applied at the chin:
- Positive: Pain on resisted protrusion strongly implicates lateral pterygoid TrPs
- Note: Studies show that 27.6% of asymptomatic subjects are tender to intraoral digital palpation of the lateral pterygoid, but none found resisted protrusion painful — this makes resisted protrusion a more specific test than palpation alone, though it may miss less severe TrP activity
Trigger Point Examination
Intraoral Palpation — Inferior Division Anterior Attachment
The most direct and reliable method, but examines only the anterior attachment region of the inferior division:
- Open the mouth approximately 2 cm
- Deviate the mandible slightly laterally to the side being examined to improve clearance between the maxilla and coronoid process
- Slide the gloved finger along the outer side of the cheek pouch vestibule, squeezing between the maxilla and coronoid process, along the roots of the upper molar teeth
- Continue to reach as high as possible along the inner surface of the coronoid process
- Press inward toward the lateral pterygoid plate
Positive finding: Exquisite tenderness with active TrPs in this region.
Distinguishing lateral pterygoid from temporalis: Temporalis fibres attach to the medial aspect of the coronoid process, lateral to the palpating finger. Lateral pterygoid fibres lie medial to the finger. The patient's response to the direction of pressure distinguishes them.
Note on specificity: 27.6% of asymptomatic subjects were tender to this palpation, suggesting a significant proportion of normal individuals have latent TrPs in this muscle or that the examination produces false positives. Resisted protrusion should be used as a confirmatory test.
External Palpation — Posterior Attachment Region
With jaws separated approximately 3 cm, a posterior portion of both divisions can be approached externally through the opening between the mandibular notch and the zygomatic arch:
- The posterior attachment region at the neck of the condyle, just below the TMJ, is accessible to external palpation
- Tenderness here can easily be misinterpreted as joint tenderness
Important: Because the lateral pterygoid can only be palpated externally through the masseter, identify and inactivate any masseter TrP tenderness in the area first. TrP bands in the underlying lateral pterygoid are too deep to distinguish from masseter bands, but can be identified by their referred pain response to pressure.
Active TrPs in the temporalis or masseter may prevent sufficient mouth opening for satisfactory examination of the lateral pterygoid. Unless these are inactivated first, only the posterior attachment region can be examined.
Nerve Entrapment
The buccal nerve (from the anterior division of V3) usually passes between the two divisions of the lateral pterygoid, sometimes through the superior division. It innervates:
- The buccinator muscle
- The skin of the cheek overlying it
- The adjacent mucous membrane of the mouth
- Part of the gum
Tautness of lateral pterygoid fibres from active TrPs can theoretically entrap this nerve, producing:
- Buccinator weakness
- Numbness and paraesthesias in the distribution of the buccal nerve
- A characteristic "weird tingling of the cheek area"
Differential Diagnosis
| Condition | Distinguishing features |
|---|---|
| TMJ arthritis | Lateral pterygoid TrP pain will not have the sharp localisation or intensity of joint inflammation; confirm with TMJ palpation — see Pain:TMJ_Screening_Examination |
| Tic douloureux (trigeminal neuralgia) | Lateral pterygoid pain is aching in quality; do not confuse with the electric, lancinating pain of tic douloureux |
| Sinusitis | Lateral pterygoid refers severe pain to the maxillary sinus region with autonomic secretion — confirm by identifying TrPs and reproducing pain; true sinusitis has fever, purulent discharge, and radiographic changes |
| Medial pterygoid TrPs | Medial pterygoid pain is more diffuse, involves the throat and hard palate; both often co-exist — treat lateral pterygoid first |
| TMJ disc derangement | Tongue-tip-to-palate test straightens the incisal path if lateral pterygoid is the primary cause; if path still zigzags, TMJ derangement is involved |
Associated TrPs
When the inferior division harbours active TrPs, its antagonists are likely to develop associated TrPs:
- Most vulnerable: medial and lateral pterygoid muscles on the opposite side (antagonists for lateral mandibular motion)
- Next: deep masseter and posterior temporalis fibres on the same side (antagonists for protrusion)
Treatment
Trigger Point Release
- Spray and stretch: Vapocoolant spray over the TMJ region and maxillary sinus area during jaw opening and lateral excursion stretch
- Intraoral ischemic compression: Via the intraoral palpation technique described above
- Resisted jaw opening: Reciprocal inhibition of elevator muscles — also inhibits the superior division
- Refer to dental/oral medicine if restricted opening and occlusal changes do not respond to conservative treatment
Address Perpetuating Factors
- Correct forward head posture — see Postural Assessment
- Correct tongue rest position (tip of tongue to roof of mouth, teeth slightly apart)
- Eliminate parafunctional habits — see Abusive Oral Habits
- Consider vitamin B1, B6, B12, and folic acid assessment if TrPs are recalcitrant
- Treat SCM and other neck muscles if lateral pterygoid TrPs are satellites
Address Key TrPs
If SCM or other neck muscle TrPs are present, treat these first — lateral pterygoid TrPs may resolve as satellites.
Satellite Trigger Points
- Medial pterygoid — most common co-active muscle; also contralateral lateral pterygoid
- Masseter — deep layer; antagonist for protrusion
- Temporalis — posterior fibres; antagonist for protrusion
- Sternocleidomastoid — key TrP that may activate lateral pterygoid as satellite
Related Pages
- Pain:Ear_and_TMJ — Diagnostic algorithm including lateral pterygoid
- Pain:TMJ_Screening_Examination — Full TMJ screening protocol
- Muscle:Medial_Pterygoid — Most common co-active muscle
- Muscle:Masseter — Functionally related; treat before examining lateral pterygoid
- Muscle:Temporalis — Antagonist involvement
- Muscle:Sternocleidomastoid — Potential key TrP source
References
- Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 1: The Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999. Chapter 11.