Temporomandibular joint biomechanics are important to understand the TMJ pain and dysfunction. This text discusses the relevant anatomy and biomechanics of TMJ.

1. TEMPOROMANDIBULAR JOINT
BIOMECHANICS
DR. SAMIDHA PATIL (PT)
MPT (MSK)

2. INTRODUCTION
 Temporomandibular joint is unique in both structure and
function.
 Structurally, mandible is horse-shoe shaped bone which
articulates with temporal bone.
 The most important functions of this joint is speech and
mastication.
 Type of joint: synovial (condylar joint).

3.  Articulation: mandible and temporal bone
 Lower teeth articulate with mandible and can guide or
restrict the movement
 Temporal bone: lateral wall of the cranium
 Styloid process: projects inferiorly
 Stylomastoid foramen: exit of facial nerve
 Mandible:
 2 ramus
 Angle of ramus
 Easily palpable
RELEVANT ANATOMY

4.  Articular surfaces:-
 Superior(Temporal bone)
- Articular tubercle
- Mandibular fossa
- Tympanic plate
 Inferior(Mandible)
- head of mandible
Main point of contact: articular eminence
Fig. 1

5.  Articular surfaces of synovial joint are generally covered with
hyaline cartilage but in TMJ the surface is covered with
fibrocartilage so it allows static and dynamic loading.

6. LIGAMENTS
Fig. 3 Fig. 4

7. ARTICULAR DISC
 Fibrous plate
 Divides the joint cavity in 2
parts
 Function:
• Increase stability
• Decrease loss of mobility
• Reduce friction
• Reduce biomechanical
stress

8.  Superior TMJ:-
- Larger
- Consists of articular eminence of temporal bone and superior surface of
disc
- Functions as gliding joint
 Inferior TMJ:-
- Consists of mandibular condyle and inferior surface of condyle
- Function as hinge joint

9.  Retrodiscal tissue:
vascular and highly innervated
Could lead to pain in TMJ
disorder when there is
inflammation and
compression

10. MOVEMENTS AT TMJ
1. Depression (open mouth)
2. Elevation ( closing mouth)
3. Protrusion (protraction of chin)
4. Retrusion ( retraction)
5. Lateral movement ( side to side movement)

12. AXIS

13. MANDIBULAR DEPRESSION AND
ELEVATION
DEPRESSION:
 Normal ROM: 35 to 55 mm
 Early stage: rolling/ rotatory movement (0 to 11- 25
mm)
- Mandibular condyle spins relative to inferior surface
in inferior joint
 Late stage: translatory movement - mandibular and disc
glide together as a complex along articular eminence in
superior joint
 Control of disc:
- med. And lat. Disc attachment of disc limit rotation
- Inf. Retrodiscal lamina limit forward excursion

14.  ELEVATION
Condyles rotated posteriorly on disc in lower
joint
 Condyle disc complex translates posteriorly in
upper joint.
 Control of disc
 Sup. Retrodiscal lamina apply post. Distractive
forced
 Eccentric control of sup. Lateral pterygoid
muscle

15. MANDIBULAR PROTRUSION AND
RETRUSION
 During protrusion: (ROM: 3- 6mm) Condyle disc translates in anterior
inferior direction following downward slope of articular eminence.
 During retrusion: (ROM: 3- 4mm) returns posterior superior path.

16.  Control of disc
 During protrusion: retrodiscal tissue stretch upto 6 to 9mm to
complete the motion
 During retrusion: limited by temporomandibular ligament and
compression of retrodiscal tissue

17. MANDIBULAR LATERAL EXCURSION
 Normal ROM: 0 to 10- 15mm
 Ipsilateral mandibular condyle spins
around a vertical axis within
mandibular fossa, while contralateral
mandibular condyle translates
anteriorly along the articular
eminence.

18. SUMMARY
MOVEMENT AXIS PLANE
Depression/Elevation Transverse/hinge Sagittal
Protrusion/Retrusion Vertical Transverse
Lateral excursion Sagittal/ ant-post Frontal

19. ASSYMETRICAL MOVEMENTS
 Rotating one condyle around anterior posterior axis while the other
condyle depresses
 It takes place in frontal plane with chin moving downwards and deviating
from midline and towards the condyle which is spinning
 Ex. Chewing and grinding movements

20. MUSCLES
I. PRIMARY MUSCLES
 Temporalis:
- Origin : Temporal fossa
- Insertion : coronoid process
- Action: Elevation, lateral excursion,
post. Fibers retraction of
protruded mandible

21.  Masseter:
- origin: Zygomatic arch and
zygomatic bone
- Insertion: external surface of
ramus of mandible
- Action: elevation (close mouth to
bite), Superficial fibers
protrusion

22.  Lateral pterygoid:
- origin: i) upper head: intra-temporal
surface and sphenoid bone
ii) Lower head: pterygoid plate
- Insertion: pterygoid fossa (neck of
mandible)
- Action: depresses mandible (open
mouth), protrude mandible, grinding
movement

23.  Medial pterygoid:
- Origin: maxilla
- Insertion: Internal surface of ramus
near angle of mandible
- Action: side excursion, elevation

24. II. SECONDARY MUSCLES:
 Suprahyoid muscles:
i. Digastric
ii. Geniohyoid
iii. Mylohyoid
iv. Stylohyoid
 Function: mandibular
depression

25.  Infrahyoid muscles:
i. Omohyoid
ii. Sternohyoid
iii. Sternothyroid
iv. thyrohyoid
 Function: stabilizing
hyoid

26. COORDINATED MUSCLE ACTION
ACTION MUSCLES
Depression Concentrically: Bilateral digastric, lateral pterygoid
Elevation Concentrically: B/L masseter, temporalis, medial pterygoid
Protrusion Lateral and medial pterygoid, B/L masseter
Retrusion Temporalis (Posterior fibers), masseter (vertical fibers)
Lateral excursion Unilateral action: medial and lateral pterygoid (opposite side deviation)
Temporalis (same side deviation)

27. REFERENCES
 B. D. Chourasia, Human anatomy, head-neck-brain; vol.3, 6th edition.
 K. L. Pamela, C. Norkins, Joint structure and function; 5th edition.
 C. Kisner, L. A. Colby, Therapeutic Exercise, 6th edition.
 C. A. Oatis, Kinesiology: The mechanics and pathomechanics of human
movements, 3rd edition.

28. THANK YOU