1. The Temporomandibular Joint
Chapter 24
The Temporomandibular Joint

2. Overview
The stomatognathic system comprises the temporomandibular joint (TMJ), the masticatory systems, and the related organs and tissues such as the salivary glands
Due to the proximity of this system with the other structures of the head and neck, an intimate relationship exists
This relationship begins in the early stages of human embryology

3. ANATOMY

4. Bones
Mandible
Maxilla
Zygomatic arch
Temporal bone

5. Temporomandibular Joint
The articular surfaces of the temporomandibular joint are lined by fibrous tissue - this reflects the development of the joint
Unlike all other synovial joints whose articular surfaces develop endochondrally and are therefore lined by hyaline cartilage, the temporomandibular joint develops in membrane

6. Intra-articular Disc Fibrous in structure
Divides the joint cavity into two regions
Thinnest centrally
Attaches anteriorly to the lateral pterygoid
Attaches posteriorly to the condyle

7. Joint Capsule
Capsular ligaments – fibers only pass between the temporal bone and mandible on the lateral side
Intrinsic ligaments – short fibers which pass from the bone to the intra-articular disc

8. Ligamentous support
Lateral TMJ ligament
Stylomandibular ligament

9. Muscles Lateral pterygoid Origin –
Upper head arises from the infratemporal surface of the greater wing of the sphenoid
Lower head arises from the lateral surface of the lateral pterygoid plate
Insertion - The anterior aspect of the neck of the mandibular condyle and capsule of the TMJ
Innervation - A branch of the mandibular division of the trigeminal nerve
Function
Upper head - involved mainly with chewing, and functions to anteriorly rotate the disc on the condyle during the closing movement
Lower head - exerts an anterior, lateral, and inferior pull on the mandible, thereby opening the jaw, protruding the mandible, and deviating the mandible to the opposite side

10. Muscles Medial pterygoid
Origin - Deep origin situated on the medial aspect of the mandibular ramus
Insertion - The inferior and posterior aspects of the medial subsurface of the ramus and angle of the mandible
Innervation - A branch of the mandibular division of the trigeminal nerve
Function - Working bilaterally - assists in mouth closing. Working unilaterally – deviation of the mandible toward the opposite side

11. Muscles Masseter - two-layered quadrilateral shaped muscle. Origin
The superficial portion arises from the anterior two-thirds of the lower border of the zygomatic arch
The deep portion arises from the medial surface of the zygomatic arch.
Insertion - On the lateral surface of the coronoid process of the mandible, upper half of the ramus and angle of the mandible
Innervation - A branch of the mandibular division of the trigeminal nerve
Function - The major function of the masseter is to elevate the mandible, thereby occluding the teeth during mastication.

12. Muscles
Tempororalis
Origin - The floor of the temporal fossa and temporal fascia
Insertion - On the anterior border of the coronoid process and anterior border of the ramus of the mandible
Innervation - A branch of the mandibular division of the trigeminal nerve
Function - assists with mouth closing/side-to-side grinding of the teeth. Also provides a good deal of stability to the joint

13. Muscles
Digastric
Origin - The posterior belly arises from the mastoid, or digastric, notch immediately behind the mastoid process of the temporal bone.
Insertion - The posterior belly passes downwards and forwards towards the hyoid bone where it becomes the intermediate digastric tendon and joins with the anterior belly.
Nerve Supply - derived from the digastric branch of the facial nerve.
Vasculature - arterial blood supply from the posterior auricular and occipital arteries.
Action - The muscle depresses the mandible and can elevate the hyoid bone. The posterior bellies act in unison and are particularly active during swallowing and chewing.

14. BIOMECHANICS

15. Biomechanics
TMJ motions involve a combination of rolls and glides of the mandibular head and disc
All TMJ motions involve all or some of the following:
Anterior/posterior glide
Medial/lateral glide
Inferior/posterior glide

16. Opening and closing Mouth opening Mouth closing Anterior glide
Lateral glide
Inferior glide
Mouth closing
Posterior glide
Medial glide
Superior glide

17. Lateral Deviation Contralateral deviation Ipsilateral deviation
Anterior, inferior and lateral glide of the mandibular head and disc
Ipsilateral deviation
Posterior, superior and medial glide of the mandibular head and disc

18. Protrusion and Retrusion
Anterior, inferior and lateral glide of the mandibular head and disc
Retrusion
Posterior, superior and medial glide of the mandibular head and disc

19. EXAMINATION

20. Examination
As with any other synovial joint, there are a number of possible causes/scenarios:
Local cause
Referred cause
Loss of motion with or without pain
Excessive motion with or without pain

21. History
There are three cardinal features of temporomandibular disorders (TMD):
Restricted jaw function (intermittent or progressive)
Joint noise (significant if associated with other factors)
Orofacial pain (Pain that is centered immediately in front of the tragus of the ear and projects to the ear, temple, cheek, and along the mandible is highly-diagnostic for TMD)
It is important to observe the patient’s mouth while they talk

22. History Attempt to determine a specific mechanism:
Trauma (including surgery – “controlled trauma”)
Posture
Emotional factors
Parafunctional habits (cheek biting, nail biting, pencil chewing, teeth clenching (day), bruxism (night))
Symptom-provoking motions of the TMJ or neighboring joint(s)

23. History The patient’s past dental and orthodontic history
Whether the patient has experienced any “locking” of the jaw
Whether the symptoms are improving or worsening

24. History Systems review
Pain or dysfunction in the orofacial region can often be due to non-musculoskeletal causes:
Otolaryngologic disease
Neurologic disease
Vascular disease
Neoplastic, and infectious disease
Psychogenic disease

25. Observation
The forward head posture is frequently associated with TMD…..try it
A lateral deviation of the jaw, evidenced by a malalignment or malocclusion of the upper and lower teeth, may cause an adaptive shortening of the mastication muscles on one side, and a lengthening of the mastication muscles on the contralateral side.

26. Observation
Cavities, wear patterns, and restored and missing teeth should be noted
Tooth wear and fracture are often destructive signs of parafunctional habits
The rest position of the TMJ should be noted
The rest position of the TMJ is determined by gently placing the little finger with the palmar portion facing anteriorly into the external auditory meatus. From an open mouth position, the patient is asked to slowly close their mouth. At the point of the resting position, the patient’s mandibular heads should be felt to gently touch the finger.

27. Range of Motion
The range of motion of the cervical spine, craniovertebral joints and the shoulders should be assessed
The range of motion of the neck and jaw should then be assessed:
Active range of motion with passive overpressure to assess the end feel.

28. Range of Motion
All movements should be smooth and without noise or pain
If pain occurs, a determination should be made as to where in the range the pain occurs, and the location of the pain
The type and temporal sequence of joint clicking can provide the clinician with information

29. Joint Noise
Reciprocal clicking is defined as clicking that occurs during opening and again during closing.
Early clicking usually indicates a small anterior displacement
Late clicking usually indicates that the disc has been further displaced
Often due to articular hypermobility, and is accompanied by a deviation of the jaw toward the contralateral side.

30. Mouth Opening
Mouth opening is the most revealing and diagnostic movement for TMD
Normal motion tested using knuckle test (approximately a two-three-knuckle width of the non-dominant hand) or more objectively by measuring (closer to 40 mm)
A limited opening of the jaw may indicate joint hypomobility, muscle tightness, or the presence of trigger points within the elevator muscles: the temporalis, masseter and medial pterygoid
Other causes of diminished mandibular opening include structural disorders of the TMJ, such as ankylosis, internal derangements, and gross osteoarthritis

31. C and S Curves
A ‘C-pattern’ of motion occurs if the hypomobility is due to internal derangement
The mandible deviates toward the involved side in the midrange of opening before returning to normal.
An ‘S-pattern’ of movement while opening the mouth may indicate a muscle imbalance. An arc may indicate a muscle imbalance
Lateral excursion of the mandible with mouth opening implicates contralateral structures such as the contralateral disc, masseter, temporalis, lateral pterygoid, or the lateral ligaments

32. Palpation
Palpation of the TMJ is used to assess tenderness, skin temperature, muscle tone, swelling, skin moisture, and the location of trigger points
Palpations of the lateral and posterior aspects of the temporomandibular joints are performed bilaterally and simultaneously

33. Strength Testing
It is important to be able to selectively stress the muscles of mastication and facial expression to determine whether they are implicated in the symptoms

34. Ligament Stress Tests
The ligament stress tests assess the integrity of the capsule and ligaments
Positive findings include excessive motion as compared to the other side, or pain
Two structures are primarily tested:
Temporomandibular ligament
Joint capsule

35. Passive Articular Mobility
The passive articular mobility tests assess the joint glides and the end feels
Findings are compared with each side
Pain or a restricted glide are positive findings and may indicate articular involvement or a capsular restriction.
It is important to check the specific glides that are related to the loss of active motion. For example, if a patient demonstrated diminished mouth opening mouth, the combined anterior, inferior, and lateral glide is assessed for each joint.

36. Articular glides
Mouth opening, contralateral deviation, and protrusion all involve an anterior, inferior and lateral glide of the mandibular head and disc
Mouth closing, ipsilateral deviation, and retrusion all involve an posterior, superior and medial glide of the mandibular head and disc

37. Conclusions If the joint glides are normal – the joint is OK
Check ligaments and surrounding tissues
If the joint glides are restricted, the cause could indicate a joint/joint capsule restriction, a ligamentous adhesion or adaptive shortening of the surrounding tissues – need to mobilize the offending joint and re-assess
The intervention should always match the diagnosis!!

38. Articular tests Dynamic loading Joint compression
The patient bites forcefully on a cotton roll or tongue depressor on one side. This maneuver loads the contralateral TMJ.
Joint compression
The clinician, standing behind the seated or supine patient, places the fingers of each hand under each side of the mandible, with the thumbs resting on the ramus. The mandible is then tipped posteriorly and inferiorly to compress the joint surfaces

39. Neurological tests
Trigeminal sensation
Trigeminal reflex

40. INTERVENTION

41. Intervention Based on:
Stage of healing. Chronic TMD pain often occurs because of secondary factors:
A fixed head forward posture
Abnormal stress levels
Depression
Oral parafunctional habits
Structure involved

42. Acute Stage The acute patient typically demonstrates:
A capsular pattern of restriction (decreased ipsilateral opening and lateral deviation to the contralateral side), with pain and tenderness on the same side
There may be associated ligamentous damage (positive stress tests), or muscular damage (positive strength tests)

43. Acute Stage
The usual methods of decreasing inflammation are recommended: PRICEMEM
Protection
Rest
Ice
Compression
Elevation?
Manual therapy
Early motion
Medications

44. TMJ Exercises Acute stage: “6x6” exercise protocol of Rocabado
Cork exercise
Tongue positioning during mouth opening and closing

45. TMJ Exercises Functional Stage:
Strengthening exercises for the cervicothoracic stabilizers, and the scapular stabilizers
Stretching exercises for the scalenes, trapezius, pectoralis minor, and levator scapulae; and the suboccipital extensors

46. Home (Automobilization) Exercises
Mouth opening exercise
Tongue depressor exercise
Toothpick exercise
Distraction mobilization

47. Functional (Chronic) Stage
Postural and patient education should form the cornerstone of any plan of care for TMD
Psychotherapy referral
Manual techniques
Exercise
Thermal and electrotherapeutic modalities
Trigger point therapy