Temporomandibular Joint
Joints
The temporomandibular joint (TMJ) is a bilateral synovial condylar joint that permits the complex movements of jaw opening, closing, protrusion, retraction, and lateral deviation required for speech, mastication, and swallowing. It is unique in that the two sides must function as a coupled pair — dysfunction on one side invariably affects the other — and its articular disc divides it into two functionally distinct compartments.
Classification
- Type: Synovial modified condyloid (with an articular disc creating upper and lower joint compartments)
- Degrees of freedom: 3 (depression/elevation, protrusion/retraction, lateral deviation)
- Region: Craniomandibular complex (bilateral; the two TMJs and the teeth form a three-point linkage)
Articular Surfaces
- Mandibular condyle (convex): An ovoid eminence on the superior mandibular ramus. The articular surface faces superiorly and anteriorly. Covered with fibrocartilage (not hyaline cartilage — this is unusual for a synovial joint and gives the TMJ greater resistance to compressive wear).
- Mandibular fossa (temporal bone, concave): A shallow concavity on the inferior surface of the temporal bone, just anterior to the external auditory meatus. Also covered with fibrocartilage.
- Articular eminence: A convex ridge anterior to the mandibular fossa. During jaw opening, the mandibular condyle translates anteriorly and slides down the posterior slope of the articular eminence. This translation is what allows wide opening beyond the limits of pure rotation.
- Articular disc (meniscus): A biconcave fibrocartilaginous disc that divides the joint into upper and lower compartments. The disc attaches to the medial and lateral poles of the condyle and to the joint capsule. The posterior attachment (bilaminar zone / retrodiscal tissue) is highly vascularized and innervated — it is the primary source of TMJ pain. The lateral pterygoid (superior head) attaches to the anterior disc, pulling it forward during opening.
Movements and ROM
Combined rotation and translation. TMJ opening is biphasic: the first 20–25 mm is pure rotation (hinge movement) in the lower compartment around a transverse axis through the condyles. Beyond 25 mm, the condyle begins to translate anteriorly and inferiorly on the articular eminence (upper compartment glide). Both phases must be intact for full opening.
Capsular Pattern
Restriction of mouth opening (limitation of depression)
The TMJ capsular pattern is defined as limited mouth opening. Some sources also note limited lateral deviation to the contralateral side. The capsular pattern is less proportionally defined than peripheral joint patterns.
Resting Position
- Mouth slightly open, lips together, teeth not touching (freeway space)
- The condyles are seated in the mandibular fossae with 2–4 mm of space between the teeth
Close-Packed Position
- Teeth clenched (maximum intercuspation)
- Maximum condylar seating, all ligaments taut
End-Feels
| Movement |
Normal End-Feel |
Type |
| Opening |
Capsular (firm) |
Capsule, temporomandibular ligament, masticatory muscles (especially masseter and temporalis) |
| Closing |
Bony (hard) |
Teeth contact (occlusion) |
| Protrusion |
Capsular (firm) |
Posterior capsule, stylomandibular ligament |
| Lateral deviation |
Capsular (firm) |
Contralateral capsule, contralateral temporomandibular ligament |
Ligaments
Temporomandibular (Lateral) Ligament
- Attachments: Zygomatic arch → lateral and posterior mandibular condylar neck
- Function: The primary TMJ stabilizer. Resists posterior and inferior displacement of the condyle. Limits opening and retraction. It acts as a "sling" that prevents the condyle from moving posteriorly into the external auditory meatus — posterior condylar displacement compresses the highly innervated retrodiscal tissue and the auriculotemporal nerve.
Sphenomandibular Ligament
- Attachments: Spine of the sphenoid → lingula of the mandible (near the mandibular foramen)
- Function: An accessory ligament that does not directly contact the TMJ capsule. It becomes taut during protrusion and limits excessive opening.
Stylomandibular Ligament
- Attachments: Styloid process → posterior border of the mandibular angle
- Function: Limits protrusion and excessive opening. Also an accessory ligament.
Mobilization Techniques
Hands-on instruction is required. The descriptions below provide clinical reference detail for understanding and supervised practice. They are not a substitute for instructor-led technique training. Correct hand placement, force dosage, and tissue response interpretation require hands-on coaching and feedback.
General Contraindications
- Absolute: TMJ fracture (condylar or mandibular), acute TMJ dislocation (anterior dislocation — the condyle translates anterior to the articular eminence and locks; requires medical reduction), active infection, malignancy, acute inflammatory arthritis (RA with TMJ involvement)
- Relative: TMJ disc displacement with locking (do not force; use gentle techniques), acute TMD flare with significant inflammation, significant joint effusion
Inferior (Caudal) TMJ Glide (Distraction)
Purpose: Distracts the mandibular condyle from the fossa, decompressing the articular surfaces and retrodiscal tissue. The most commonly used TMJ mobilization — appropriate for general TMJ stiffness, TMD pain, and as a starting technique for any TMJ restriction.
Patient position:
- Supine on the treatment table
- Head supported, neck in neutral
- Mouth slightly open (resting position)
Hand placement:
- Stabilizing hand: Cups the cranium, stabilizing the head against the table
- Mobilizing hand: Gloved thumb placed intraorally on the inferior molars on the affected side (or the mandibular alveolar ridge). The thumb pad rests on the lower teeth/ridge. The index finger supports the mandible externally from below. Force directed inferiorly (caudally, toward the patient's feet).
Technique execution:
- Apply a slow, sustained or oscillatory force directed inferiorly, distracting the condyle away from the fossa
- Grade I–II: Very gentle oscillations for pain modulation. TMJ structures are small and sensitive — use minimal force.
- Grade III: Sustained distraction at end-range for capsular stretch
- Duration: 15–30 seconds per set, 2–3 sets
- Reassess mouth opening between sets
Indications:
- Limited mouth opening (<35 mm interincisal distance)
- TMD pain with muscle guarding and capsular restriction
- Post-surgical TMJ stiffness (when cleared by surgeon)
Technique notes:
- Gloves are mandatory for any intraoral technique.
- Common error: Excessive force — the TMJ is a small joint; Grade I–II is usually sufficient. The patient's pain tolerance is the primary guide.
- Common error: Pressing down on the teeth rather than distracting the condyle. The force is directed inferiorly and slightly anteriorly.
- Reassessment: Re-test mouth opening (interincisal distance with a ruler).
Anterior TMJ Glide (Translation)
Purpose: Restores the anterior translation component of mouth opening. When opening is limited because the condyle does not translate anteriorly down the articular eminence (the translation phase is restricted), anterior glide restores this component.
Patient position: Same as above.
Hand placement:
- Gloved thumb intraorally on the lower molars. External hand supports the mandible. Force directed anteriorly (toward the patient's nose).
Technique execution:
- Apply an oscillatory force directed anteriorly, translating the condyle anteriorly and inferiorly on the articular eminence
- Grade I–II: Gentle oscillations — the retrodiscal tissue is compressed during posterior condylar position; anterior translation decompresses it
- Grade III: Oscillations into the translation end-range
- Duration: 15–30 seconds, 2–3 sets
Indications:
- Limited mouth opening with restricted translation phase (opening stops at ~25 mm — rotation occurs normally but translation is blocked)
- Anterior disc displacement without reduction (the disc blocks anterior condylar translation — proceed very gently)
Technique notes:
- Disc displacement consideration: In anterior disc displacement without reduction ("closed lock"), the displaced disc physically blocks condylar translation. Gentle anterior glide may help the condyle recapture the disc, but this requires careful technique and should not be forced.
- Reassessment: Re-test active opening. If opening improves beyond 25 mm, the translation component was the restriction.
Muscles Crossing This Joint
Muscles of Mastication
- anatomy/muscles/masseter — the most powerful jaw closer; superficial and deep heads; frequently hypertonic in bruxism and TMD
- anatomy/muscles/temporalis — jaw closing (entire muscle) and retraction (posterior fibers); its broad fan shape allows force production throughout the ROM
- anatomy/muscles/medial-pterygoid — jaw closing, protrusion, lateral deviation to the opposite side
- anatomy/muscles/lateral-pterygoid — inferior head: jaw opening (depression) and protrusion; superior head: disc control during closing. The lateral pterygoid is the only muscle of mastication that opens the jaw.
Suprahyoid Muscles (Jaw Openers)
- anatomy/muscles/digastric — opens the jaw when the hyoid is fixed; anterior belly (mylohyoid nerve/CN V3) and posterior belly (facial nerve/CN VII)
- anatomy/muscles/mylohyoid — floor of the mouth; assists jaw opening
- anatomy/muscles/geniohyoid — assists jaw opening and protrusion
Conditions Affecting This Joint
- Temporomandibular disorder (TMD) — umbrella term for TMJ and masticatory muscle pain; the most common non-dental cause of orofacial pain; presents with jaw pain, clicking, limited opening, headache
- Anterior disc displacement with reduction — the disc displaces anteriorly at rest; during opening, the condyle "recaptures" the disc (producing a click); the disc displaces again during closing (producing a second click — reciprocal clicking)
- Anterior disc displacement without reduction — "closed lock"; the disc does not recapture during opening; produces sudden limited opening (<25–30 mm) with no click (the click that was previously present disappears)
- TMJ osteoarthritis — degenerative changes to the condyle and fossa; crepitus, morning stiffness, progressive opening limitation
- Bruxism — habitual teeth clenching or grinding; produces masticatory muscle hypertonia, TMJ compression, tooth wear, and headache
- TMJ dislocation — anterior dislocation (condyle translates anterior to the articular eminence and locks in an open position); requires medical reduction
Clinical Notes
- TMD is multifactorial. It is rarely purely articular or purely muscular. Most TMD presentations involve a combination of capsular restriction, disc displacement, masticatory muscle hypertonia, occlusal factors, and psychosocial contributors (stress, anxiety, sleep bruxism). Treatment must address multiple factors.
- Clicking does not necessarily mean treatment is needed. Approximately 30% of the asymptomatic population has TMJ clicking. Painless clicking that does not limit function generally does not require intervention. Painful clicking, progressive locking, or worsening opening limitation does require treatment.
- The masseter and temporalis are the primary targets for muscle treatment in TMD. Both muscles are frequently hypertonic from bruxism and stress-related clenching. Intraoral and extraoral techniques targeting these muscles often produce significant symptomatic improvement.
- Always assess cervical spine involvement. The cervical spine and TMJ are biomechanically and neurologically linked. Forward head posture changes mandibular resting position and increases masseter/temporalis activity. Cervicogenic headache and TMD headache frequently coexist. Treat both regions.
Key Takeaways
- TMJ opening is biphasic — the first 25 mm is rotation (lower compartment); beyond 25 mm is translation (upper compartment). Identify which phase is restricted to select the appropriate technique.
- The retrodiscal tissue is the primary TMJ pain source — it is highly vascularized and innervated; posterior condylar compression (bruxism, posterior disc displacement) produces pain.
- Normal opening is 35–55 mm (interincisal distance) — less than 35 mm indicates restriction requiring assessment.
- Always assess the cervical spine in TMD — forward head posture alters mandibular position and masticatory muscle activity.
