Lesson 3: TMJ Kinesiology

True or False
The TMJ is synovial?

- True

What type of Joint is the TMJ?

- Ginglymoarthrodial

True or False
The TMJ is load bearing?

- True

True or False
The TMJ has a superior & inferior joint?

- True

What type of joint is the Inferior Joint of the TMJ?

- Ginglymo, which also can be called (Hinged Shape)

What is in Articulation within the Inferior Joint of the TMJ?

- Mandibular Condyle & Inferior surface of the Disc

What type of joint is the Superior Joint of the TMJ?

- Arthrodial (synovial & gliding)

What is in Articulation within the Superior Joint of the TMJ?

- Articular Eminence & the Superior surface of the Disc

What type of Cartilage is lined within the Condyles & Articular Eminence of the TMJ?

- Fibrocartilage

True or False
The condyles & articular eminence are vascular & neural?

False
- They are Avascular & Aneural

Within the articular disc of the TMJ, 3 bands exist, name these 3 bands?

- Anterior Band

- Posterior Band

- Intermediate Band

Describe the Anterior Band of the articular disc?

- Periphery Vascular & Neural

Describe the Posterior Band of the articular disc?

- Periphery Vascular & Neural

- It is also the THICKEST band within the disc

Describe the Intermediate Band of the articular disc?

- Avascular & Aneural

- It is the THINNEST of the 3 bands

- It is Load Bearing

- It's position is maintained with the condyle & articular eminence during MOVEMENT

Describe the Anterior Attachment of the Articular Disc?

- Capsule/Lateral Pterygoid (superior division) tendon

Describe the Medial/Lateral Attachment within the Articular Disc?

- At the condyle via the collateral ligaments

Describe the Posterior Attachment within the Articular Disc?

- Superior/Inferior Lamina to posterior mandibular fossa/tubercle & to the neck of the condyle

Where is the Retrodiscal Pad?

- Between the Lamina

What does the Retrodiscal Pad contain? (Hint: 6 items)

- Collagen Fibers
- Elastic Fibers
- Fat Deposits
- Neural Components
- Vascular Components
- Lymphatics

What fills the mandibular fossa during translation?

- Retrodiscal Pad

What do we usually suspect to have a potential site of inflammation?

- Retrodiscal Pad

What is the Purpose of the Retrodiscal Pad? (Hint: there are 5)

- Maintain Joint Congruency (convex on convex)

- Increase Stability

- Maximize Mobility

- Reduce Friction

- Decreases stress at the joint

What is the Function of the Lateral Ligament?

- Protect Posterior Attachment

- Restrains Maximal Condyle Movement

- Assist Transition Rotation to Translation

List our Two extracapsular ligaments?

- Sphenomandibular

- Stylomandibular

What is the Function of the Extracapsular Ligaments of the TMJ?

- Joint Protection within EXTREME movement

What is the attachment of the Anterior Malleolar Ligament?

- Sphenoid Bone & the Medial capsule to the malleus, which is known as the ossicle in the middle ear

What is the Function of the Anterior Malleolar Ligament?

- We really don't know, some say that it is the reason for ear symptoms in those who experience a TMJ injury

What Muscles are working when the motion "Protrusion" is activated?

- Lateral pterygoid assisted by the medial pterygoid

What Muscles are working when the motion "Retraction" is activated?

- Posterior fibers of the Temporalis

- Deep part of the Masseter

- Geniohyoid & Digastric muscles are also helping

What Muscles are working when the motion "Elevation" is activated?

- Temporalis
- Masseter
- Medial Pterygoid

What Muscles and or Forces are working when the motion "Depression" is activated?

- Gravity
- Digastric
- Geniohyoid
- Mylohyoid

What Muscles are working when the motion "Lateral Excursion" is activated?

- Lateral (inferior) Pterygoid & Medial Pterygoid

What does Elevation mean within the TMJ?

- Closing of the mouth

What does Depression mean within the TMJ?

- Opening of the mouth

What is the Plane and Axis of Elevation?

Plane:
- Sagittal

Axis:
- Medial/Lateral

What is the Plane and Axis of Depression?

Plane:
- Sagittal

Axis:
- Medial/Lateral

What is the Plane and Axis of Protrusion?

Plane:
- Sagittal

Axis:
- There is no axis

What is the Plane and Axis of Retraction?

Plane:
- Sagittal

Axis:
- There is no axis

Why do we see No Axis within movements of Protrusion, Retraction, & sometimes Lateral Excursion?

- This is due to the movement producing a Glide Motion

What is the Plane and Axis of Lateral Excursion?

Plane:
- Transverse

Axis:
- Pure movement of lateral excursion has no axis, however, if we are CHEWING then the axis becomes VERTICAL

True or False
There are two phases of opening (depression) within the TMJ? If so, what are these two phases?

- True

Two Phases:
- Roll & Glide

What is the First Phase of Opening (Depression)?

- Roll

How many millimeters do we see within the 1st Phase of the Opening (depression) movement?

- Ten to Eleven Millimeters

Describe how the "Roll" occurs within the 1st phase of Opening (depression)?

- Onset of opening to midpoint

- Condyle rotates on the undersurface of the disc at the LOWER COMPARTMENT

- Collateral ligaments gradually tighten, which ultimately, assists in transition to the 2nd Phase

Within the 2nd Phase of Opening (depression), is it classified as a Roll or Glide?

- It is a Glide

How many Millimeters do we see within the motion Opening (depression) of the 2nd Phase which happens to glide?

- Thirty Millimeters

Describe the Glide within the 2nd Phase of Opening (Depression)?

- Anterior & slightly caudal translation of the Condyle & Disc under articular eminence (protrusion) at the UPPER COMPARTMENT

- Contraction of the inferior lateral pterygoid assists dynamically

True or False
In the opening (depression) movement, we see that NO FURTHER ROTATION occurs once anterior translation begins?

- True

If anterior translation is not available within the Opening (depression) movement, what then would occur?

- One side of the chin would deviate ipsilaterally

True or False
With the opening motion of the TMJ, we first roll then we glide?

- True

Define Protrusion?

- Forward movement of the mandible

Where does Anterior Translation occur within the motion "Protrusion"?

- In the Upper Compartment of the joint

Describe how the mandible moves during Protrusion?

- It moves forward but it also moves slightly downward as the mandible is pressed down on the articular eminence

Describe how the motion "Elevation (closing)" happens within the TMJ?

- Condyles glide backward (posterior) & then hinge on the menisci

Describe what the Inferior & Superior heads of the lateral pterygoid do during Elevation?

Inferior Head:
- Relaxes

Superior Head:
- Contracts pulling disc antero-medial on the condyle

Define Retrusion?

- Backward movement of the mandible

During Retrusion, what muscles & elevators synergistically balance each other out to keep the jaw in a horizontal position?

- Geniohyoid
- Digastric

How many Millimeters do we see within the motion "Lateral Excursion"?

- Five to Seven Millimeters

Describe Lateral Excursion?

- Lateral movement of the mandible in the horizontal plane

- Also called Rotation

- Motion is necessary for chewing & grinding

Explain the biomechanical aspects of Grinding Movements?

- Mandible rotates about a vertical axis through the mandibular head by unilateral contraction of the lateral pterygoid muscle

- Followed by contraction of the posterior temporalis muscle which repositions the condyle

What is the Open Packed position of the TMJ?

- It is known as the Rest Position

Describe the Open Packed position of the TMJ?

- Position the jaw assumes when there is Minimal Muscle Action Potential

- The head is in a normal upright resting position

- Resting tonus, no occlusal contact

Where is the Tongue within the Open Packed Position of the TMJ?

- Up against the palate of the mouth

What is the Closed Packed Position of the TMJ?

- Known as Centric Occlusion

Describe the Closed Packed Position of the TMJ?

- Jaws are closed so all upper & lower teeth meet

- Results in full occlusion with balanced intercuspation of the upper & lower dental arches

True or False
The jaw can move forward, laterally, & backwards to a limited extent in "normal jaws"?

- True

What is Malocclusion?

- Absent or abnormally positioned teeth that can cause a displacement within the mandible from normal central occlusion

What does Malocclusion result in?

- Results in disturbance of balance between teeth

- Disturbs balance between TMJ's & Musculature