Muscles of Mastication - Palpation Techniques

1. MASSETER

Extraoral Palpation

• Ask the patient to clench their teeth - this causes the masseter to contract visibly and become firm, making it easy to locate.
• Place your index fingers bilaterally over the body of the muscle on the lateral surface of the ramus.
• The body can also be pinched between thumb and index finger to assess the full thickness of the muscle.
• Palpate from the origin at the zygomatic arch down to the insertion at the gonial angle.
• Palpate the deep head separately by placing the finger just below the zygomatic arch with the mouth open (puts the muscle under tension).
• Assess for tenderness, tightness, and trigger points.

Intraoral Palpation

• Place the index finger inside the mouth along the anterior border of the mandibular ramus.
• The deep portion of the masseter inserts at the gonial angle region and can be palpated from within the oral cavity.
• Ask the patient to open wide to relax the muscle, then palpate along the inner aspect of the ramus.
• Tenderness along the anterior border of the ramus intraorally is clinically significant for TMJ dysfunction even in patients with no jaw complaints.

From Shambaugh Surgery of the Ear: "Intraoral examination for tenderness of the masseter and temporalis muscles along the anterior border of the mandibular ramus is often revealing for TMJ dysfunction, despite a negative history of jaw problems."

2. TEMPORALIS

Extraoral Palpation

• Ask the patient to clench to locate and confirm the muscle.
• Palpate bilaterally and systematically in three regions:
  • Anterior fibers: at the temple above the zygomatic arch, just above and lateral to the orbital rim
  • Middle fibers: mid-temporal fossa region
  • Posterior fibers: above and behind the ear, near the hairline
• Palpate at rest first, then during clenching and during jaw opening.
• Tenderness here commonly refers pain to the maxillary posterior teeth, above the eye, and to the temporal region (tension-type headaches).

Intraoral Palpation (Tendon)

• Open the mouth to expose the coronoid process and retromolar area.
• Place the fingertip at the anteromedial portion of the ramus at the retromolar pad level and trace upward to the coronoid process.
• This palpates the temporalis tendon insertion - a frequent site of tenderness in bruxism and TMD.
• From Shambaugh: tenderness along the anterior border of the ramus intraorally includes the temporalis tendon region.

From Scott-Brown's: "The temporalis lies above the zygomatic arch, extending behind and above the ear and onto the forehead below the hairline. Tenderness in a muscle during clenching or the palpation of tight bands of muscle indicates myofascial spasm and pain."

3. MEDIAL PTERYGOID (Internal Pterygoid)

Extraoral Palpation

• Limited access. Can be approached by palpating medial to the mandibular angle from outside, but this is unreliable and uncomfortable.
• The ipsilateral medial pterygoid is a useful indirect indicator of lateral pterygoid overuse - when the lateral pterygoid is hyperactive (as in bruxism), the medial pterygoid (its antagonist) becomes tender.

Intraoral Palpation (Primary route)

• With the patient's mouth partially open (relaxed, not wide open):
  • Step 1: Place the examining finger at the anteromedial ramus (retromolar area) - same start as temporalis tendon palpation.
  • Step 2: Ask the patient to gently close and press your finger laterally against the medial surface of the ramus to palpate the medial pterygoid muscle belly.
  • Step 3: Ask the patient to open again and palpate lower - at the angle of the mandible on the inner (lingual) side, below the lower third molar region.
• Ask beforehand if the patient has a strong gag reflex.
• Tenderness here is closely associated with referred otalgia in TMJ dysfunction.

From Scott-Brown's Vol 2: "Intraoral palpation of the lateral and medial pterygoids frequently reveals tenderness, and this finding is more commonly seen in patients with referred otalgia."

4. LATERAL PTERYGOID (External Pterygoid)

Extraoral Palpation

• Essentially inaccessible extraorally due to its deep position within the infratemporal fossa, medial to the coronoid process.
• Functional test (indirect): Place your thumb on the patient's chin and ask them to protrude the jaw against resistance. Pain on the side of resistance indicates lateral pterygoid dysfunction on that side.
• This is the most reliable extraoral assessment method.

Intraoral Palpation (Only route)

• This is the most challenging palpation among the masticatory muscles.
• Technique:
  1. Ask the patient to open the mouth slightly (not wide - wide opening tightens tissues)
  2. Place the little finger or index finger lateral to the maxillary tuberosity and medial to the coronoid process
  3. Direct the fingertip upward, inward, and posteriorly (superiorly and medially toward the infratemporal region)
  4. Pressure is applied in this direction - a positive response (pain/tenderness) indicates muscle dysfunction
• Tenderness was found in 85% of TMJ dysfunction patients in one large clinical study.
• Note: True direct palpation of the muscle belly is debated - some authors argue the finger reaches only the region near the muscle's lower head, not the full muscle.

From Scott-Brown's Vol 2: "The most reliable diagnostic clinical finding in TMJ dysfunction is tenderness of the masticatory muscles... tenderness of the lateral pterygoid reported in 85%."

Summary Table

Clinical Pearls

• Always palpate bilaterally and compare sides.
• Palpate at rest, during clenching, and during jaw movement to differentiate muscle spasm vs. joint pain.
• The masseter and temporalis are the most commonly affected muscles in TMD and bruxism.
• Intraoral palpation of the pterygoids is the most diagnostically reliable route and especially important in patients with referred otalgia.
• Tenderness of masticatory muscles is the most reliable clinical sign of TMJ dysfunction.
• Inter-incisal opening <35 mm is found in ~3% of normal adults and suggests restriction when present.