Lecture 9 TMJ anatomy examination

CLASSIFICATION
 The temporomandibular joint (TMJ) is composed of the temporal bone and the
mandible, as well as a specialized dense fibrous structure, the articular disk, several
ligaments, and numerous associated muscles.
 The TMJ is a compound joint that can be classified by anatomic type as well as by
function.
 Anatomically the TMJ is a diarthrodial joint, which is a discontinuous articulation of two
bones permitting freedom of movement that is dictated by associated muscles and
limited by ligaments.
 Its fibrous connective tissue capsule is well innervated and well vascularized and
tightly attached to the bones at the edges of their articulating surfaces. It is also a
synovial joint, lined on its inner aspect by a synovial membrane, which secretes
synovial fluid. The fluid acts as a joint lubricant and supplies the metabolic and
nutritional needs of the nonvascularized internal joint structures.
2

Functionally the TMJ is a compound joint, composed of four
articulating surfaces: the articular facets of the temporal bone
and of the mandibular condyle and the superior and inferior
surfaces of the articular disk.
The articular disk divides the joint into two compartments. The
lower compartment permits hinge motion or rotation and hence
is termed ginglymoid.
The superior compartment permits sliding (or translatory)
movements and is therefore called arthrodial. Hence the
temporomandibular joint as a whole can be termed
ginglymoarthrodial.
3

BONY STRUCTURES
The articular portion of the temporal bone is composed of
three parts.
The largest is the articular or mandibular fossa, a concave
structure extending from the posterior slope of the articular
eminence to the postglenoid process, which is a ridge
between the fossa and the external acoustic meatus.
The surface of the articular fossa is thin and may be
translucent on a dry skull. This is not a major stress-bearing
area.
4

A, Bony structures of the TMJ (lateral view). MF, mandibular fossa;
AE, articular eminence. B, articular fossa (inferior view). AE,
articular eminence; MF, mandibular fossa; STF, squamotympanic
fissure.
5

The second portion, the articular eminence, is a transverse
bony prominence that is continuous across the articular
surface mediolaterally. The articular eminence is usually
thick and serves as a major functional component of the
TMJ.
The articular eminence is distinguished from the articular
tubercle, a nonarticulating process on the lateral aspect of
the zygomatic root of the temporal bone, which serves as a
point of attachment of collateral ligaments.
The third portion of the articular surface of the temporal
bone is the preglenoid plane, a flattened area anterior to
the eminence.
6

The mandible is a U-shaped bone that articulates with
the temporal bone by means of the articular surface of
its condyles, paired structures forming an
approximately 145° to 160° angle to each other. The
mandibular condyle is approximately 15 to 20 mm in
width and 8 to 10 mm in anteroposterior dimension.
The condyle tends to be rounded mediolaterally and
convex anteroposteriorly.
On its medial aspect just below its articular surface is a
prominent depression, the pterygoid fovea, which is the
site of attachments of the lateral pterygoid muscle.
7

The condyle. (A) Anterior and (B) posterior views. A dotted line
marks the border of the articular surface. The articular surface on
the posterior aspect of the condyle is greater than that on the
anterior aspect. 8

CARTILAGE AND SYNOVIUM
 Lining the inner aspect of all synovial joints, including the TMJ, are two
types of tissue: articular cartilage and synovium. The space bound by
these two structures is termed the synovial cavity, which is filled with
synovial fluid.
 The articular surfaces of both the temporal bone and the condyle are
covered with dense articular fibrocartilage, a fibrous connective tissue.
This fibrocartilage covering has the capacity to regenerate and to
remodel under functional stresses.
 Deep to the fibrocartilage, particularly on the condyle, is a proliferative
zone of cells that may develop into either cartilaginous or osseous
tissue. Most change resulting from function is seen in this layer.
9

The temporomandibular joint
(coronal view).
10

 Articular cartilage is composed of chondrocytes and an intercellular matrix
of collagen fibers, water, and a nonfibrous filler material, termed ground
substance.
 Chondrocytes are enclosed in otherwise hollow spaces, called lacunae,
and are arranged in three layers characterized by different cell shapes.
 The superficial zone contains small flattened cells with their long axes
parallel to the surface.
 In the middle zone the cells are larger and rounded and appear in
columnar fashion perpendicular to the surface.
 The deep zone contains the largest cells and is divided by the “tide mark”
below which some degree of calcification has occurred.
 There are few blood vessels in any of these areas, with cartilage being
nourished primarily by diffusion from the synovial fluid.
11

Collagen fibers are arranged in arcades with an
interlocking meshwork of fibrils parallel to the articular
surface joining together as bundles and descending to
their attachment in the calcified cartilage between the
tide mark.
Functionally these arcades provide a framework for
interstitial water and ground substance to resist
compressive forces encountered in joint loading.
Formed by intramembranous processes the TMJ’s
articular cartilage contains a greater proportion of
collagen fibers (fibrocartilage) than other synovial
joints, which are covered instead by hyaline cartilage.
12

A histologic section of a healthy mandibular condyle showing
the four zones 13

The ground substance contains a variety of plasma proteins,
glucose, urea, and salts, as well as proteoglycans, which are
synthesized by the Golgi apparatus of the chondrocytes.
Proteoglycans are macromolecules consisting of a protein core
attached to many glycosaminoglycan chains of chondroitin
sulfate and keratan sulfate.
Proteoglycans play a role in the diffusion of nutrients and
metabolic breakdown products.
Ground substance permits the entry and release of large
quantities of water, an attribute thought to be significant in
giving cartilage its characteristic functional elasticity in
response to deformation and loading.
16

The collagen network
interacting with the
proteoglycan network
in the extracellular
matrix, forming a
fiber-reinforced
composite.
17

Lining the capsular ligament is the synovial membrane, a thin,
smooth, richly innervated vascular tissue without an epithelium.
Synovial cells, somewhat undifferentiated in appearance, serve
both a phagocytic and a secretory function and are thought to
be the site of production of hyaluronic acid, a
glycosaminoglycan found in synovial fluid.
Some synovial cells, particularly those in close approximation
to articular cartilage, are thought to have the capacity to
differentiate into chondrocytes. The synovium is capable of
rapid and complete regeneration following injury.
Recently, synovial cells (as well as chondrocytes and
leukocytes) have been the focus of extensive research
regarding the production of anabolic and catabolic cytokines
within the TMJ. 18

 Synovial fluid is considered an ultrafiltrate of plasma. It contains a high
concentration of hyaluronic acid, which is thought to be responsible for
the fluid’s high viscosity.
 The proteins found in synovial fluid are identical to plasma proteins;
however, synovial fluid has a lower total protein content, with a higher
percentage of albumin and a lower percentage of α-2-globulin.
 Alkaline phosphatase, which may also be present in synovial fluid, is
thought to be produced by chondrocytes.
 Leukocytes are also found in synovial fluid, with the cell count being less
than 200 per cubic millimeter and with less than 25% of these cells being
polymorphonuclear.
 Only a small amount of synovial fluid, usually less than 2 mL, is present
within the healthy TMJ.
19

Functions of the synovial fluid include lubrication of the joint,
phagocytosis of particulate debris, and nourishment of the
articular cartilage.
Joint lubrication is a complex function related to the viscosity of
synovial fluid and to the ability of articular cartilage to allow the
free passage of water within the pores of its glycosaminoglycan
matrix.
Application of a loading force to articular cartilage causes a
deformation at the location. It has been theorized that water is
extruded from the loaded area into the synovial fluid adjacent
to the point of contact.
The concentration of hyaluronic acid and hence the viscosity of
the synovial fluid is greater at the point of load, thus protecting
the articular surfaces.
20

As the load passes to adjacent areas the deformation
passes on as well, while the original point of contact
regains its shape and thickness through the
reabsorption of water.
Exact mechanisms of flow between articular cartilage
and synovial fluid are as yet unclear.
Nevertheless the net result is a coefficient of friction for
the normally functioning joint—approximately 14 times
less than that of a dry joint.
21

THE ARTICULAR DISK
The articular disk is composed of dense fibrous connective
tissue and is nonvascularized and noninnervated, an
adaptation that allows it to resist pressure.
Anatomically the disk can be divided into three general
regions as viewed from the lateral perspective: the anterior
band, the central intermediate zone, and the posterior band.
The thickness of the disk appears to be correlated with the
prominence of the eminence. The intermediate zone is
thinnest and is generally the area of function between the
mandibular condyle and the temporal bone.
22

Articular disc, fossa, and
condyle (lateral view). The
condyle is normally situated
on the thinner intermediate
zone (IZ) of the disc. The
anterior border of the disc
(AB) is considerably thicker
than the intermediate zone,
and the posterior border (PB)
is even thicker.
23

The temporomandibular joint (lateral view).
24

Despite the designation of separate portions of the
articular disk, it is in fact a homogeneous tissue and the
bands do not consist of specific anatomic structures.
The disk is flexible and adapts to functional demands of
the articular surfaces.
The articular disk is attached to the capsular ligament
anteriorly, posteriorly, medially, and laterally.
Some fibers of the superior head of the lateral
pterygoid muscle insert on the disk at its medial aspect,
apparently serving to stabilize the disk to the
mandibular condyle during function.
25

RETRODISKAL TISSUE
 Posteriorly the articular disk blends with a highly vascular, highly
innervated structure— the bilaminar zone, which is involved in the
production of synovial fluid.
 The superior aspect of the retrodiskal tissue contains elastic fibers and is
termed the superior retrodiskal lamina, which attaches to the tympanic
plate and functions as a restraint to disk movement in extreme translatory
movements.
 The inferior aspect of the retrodiskal tissue, termed the inferior retrodiskal
lamina, consists of collagen fibers without elastic tissue and functions to
connect the articular disk to the posterior margin of the articular surfaces
of the condyle.
 It is thought to serve as a check ligament to prevent extreme rotation of
the disk on the condyle in rotational movements.
26

RT, retrodiscal tissues; SRL, superior retrodiscal lamina (elastic); IRL, inferior retrodiscal
lamina (collagenous); ACL, anterior capsular ligament (collagenous); SLP and ILP, superior
and inferior lateral pterygoid muscles; AS, articular surface; SC and IC, superior and
inferior joint cavity; the discal (collateral) ligament has not been drawn. 27

LIGAMENTS
Ligaments associated with the TMJ are composed of
collagen and act predominantly as restraints to motion of the
condyle and the disk.
Three ligaments—collateral, capsular, and
temporomandibular ligaments— are considered functional
ligaments because they serve as major anatomic
components of the joints.
Two other ligaments—sphenomandibular and
stylomandibular— are considered accessory ligaments
because, although they are attached to osseous structures at
some distance from the joints, they serve to some degree as
passive restraints on mandibular motion.
28

The collateral (or diskal) ligaments are short paired
structures attaching the disk to the lateral and medial
poles of each condyle. Their function is to restrict
movement of the disk away from the condyle, thus
allowing smooth synchronous motion of the disk-
condyle complex.
Although the collateral ligaments permit rotation of the
condyle with relation to the disk, their tight attachment
forces the disk to accompany the condyle through its
translatory range of motion.
29

The capsular ligament encompasses each joint, attaching
superiorly to the temporal bone along the border of the
mandibular fossa and eminence and inferiorly to the neck of
the condyle along the edge of the articular facet.
It surrounds the joint spaces and the disk, attaching anteriorly
and posteriorly as well as medially and laterally, where it blends
with the collateral ligaments.
The function of the capsular ligament is to resist medial,
lateral, and inferior forces, thereby holding the joint
together. It offers resistance to movement of the joint
only in the extreme range of motion. A secondary function of
the capsular ligament is to contain the synovial fluid within the
superior and inferior joint spaces.
31

Capsular ligament (lateral view).
32

The temporomandibular (lateral) ligaments are located on
the lateral aspect of each TMJ. Unlike the capsular and
collateral ligaments, which have medial and lateral components
within each joint, the temporomandibular ligaments are single
structures that function in paired fashion with the
corresponding ligament on the opposite TMJ. Each
temporomandibular ligament can be separated into two distinct
portions, that have different functions.
The outer oblique portion descends from the outer aspect of
the articular tubercle of the zygomatic process posteriorly and
inferiorly to the outer posterior surface of the condylar neck. It
limits the amount of inferior distraction that the condyle may
achieve in translatory and rotational movements.
33

Temporomandibular joint (lateral
aspect)
34

The inner horizontal portion also arises from the
outer surface of the articular tubercle, just medial to the
origin of the outer oblique portion of the ligament, and
runs horizontally backward to attach to the lateral pole
of the condyle and the posterior aspect of the disk.
The function of the inner horizontal portion of the
temporomandibular ligament is to limit posterior
movement of the condyle, particularly during pivoting
movements, such as when the mandible moves
laterally in chewing function. This restriction of posterior
movement serves to protect the retrodiskal tissue.
35

The sphenomandibular ligament arises from the spine of the
sphenoid bone and descends into the fan-like insertion on the
mandibular lingula, as well as on the lower portion of the
medial side of the condylar neck. The sphenomandibular
ligament serves to some degree as a point of rotation during
activation of the lateral pterygoid muscle, thereby contributing
to translation of the mandible.
The stylomandibular ligament descends from the styloid
process to the posterior border of the angle of the mandible
and also blends with the fascia of the medial pterygoid muscle.
It functions similarly to the sphenomandibular ligament as a
point of rotation and also limits excessive protrusion of the
mandible.
36

Temporomandibular ligament (medial
view). 37

VASCULAR SUPPLY AND
INNERVATION
 The vascular supply of the TMJ arises primarily from branches of the
superficial temporal and maxillary arteries posteriorly and the
masseteric artery anteriorly.
 There is a rich plexus of veins in the posterior aspect of the joint
associated with the retrodiskal tissues, which alternately fill and empty
with protrusive and retrusive movements, respectively, of the condyle
disk complex and which also function in the production of synovial fluid.
 The nerve supply to the TMJ is predominantly from branches of the
auriculotemporal nerve with anterior contributions from the
masseteric nerve and the posterior deep temporal nerve. Many of the
nerves to the joint appear to be vasomotor and vasosensory, and they
may have a role in the production of synovial fluid.
38

MUSCULATURE
All muscles attached to the mandible influence its movement
to some degree. Only the four large muscles that attach to
the ramus of the mandible are considered the muscles of
mastication; however, a total of 12 muscles actually influence
mandibular motion, all of which are bilateral. Muscle pairs
may function together for symmetric movements or
unilaterally for asymmetric movement.
For example, contraction of both lateral pterygoid muscles
results in protrusion and depression of the mandible without
deviation, whereas contraction of one of the lateral pterygoid
muscles results in protrusion and opening with deviation to
the opposite side. 39

 Muscles influencing mandibular motion may be divided into two groups by
anatomic position. Attaching primarily to the ramus and condylar neck of
the mandible is the supramandibular muscle group, consisting of the
temporalis, masseter, medial pterygoid, and lateral pterygoid muscles.
 This group functions predominantly as the elevators of the mandible. The
lateral pterygoid does have a depressor function as well. Attaching to the
body and symphyseal area of the mandible and to the hyoid bone is the
inframandibular group, which functions as the depressors of the mandible.
The inframandibular group includes the four suprahyoid muscles
(digastric, geniohyoid, mylohyoid, and stylohyoid) and the four infrahyoid
muscles (sternohyoid, omohyoid, sternothyroid, and thyrohyoid).
 The suprahyoid muscles attach to both the hyoid bone and the mandible
and serve to depress the mandible when the hyoid bone is fixed in place.
They also elevate the hyoid bone when the mandible is fixed in place. The
infrahyoid muscles serve to fix the hyoid bone during depressive
movements of the mandible.
40

SUPRAMANDIBULAR MUSCLE
GROUP
 The temporalis muscle is a large fan-shaped muscle taking its origin
from the temporal fossa and lateral aspect of the skull, including
portions of the parietal, temporal, frontal, and sphenoid bones. Its fibers
pass between the zygomatic arch and the skull and insert on the
mandible at the coronoid process and anterior border of the ascending
ramus down to the occlusal surface of the mandible, posterior to the
third molar tooth.
 Viewed coronally the temporalis muscle has a bipennate character in
that fibers arising from the skull insert on the medial aspect of the
coronoid process, whereas fibers arising laterally from the temporalis
fascia insert on the lateral aspect of the coronoid process.
41

A, Temporal muscle. AP, anterior portion; MP, middle
portion; PP, posterior portion.
B, Function: elevation of the mandible. The exact
movement is indicated by the location of the fibers or
portion being activated. 42

In an anteroposterior dimension the temporalis muscle consists
of three portions: the anterior, whose fibers are vertical; the
middle, with oblique fibers; and the posterior portion, with
semihorizontal fibers passing forward to bend under the
zygomatic arch.
The function of the temporalis muscle is to elevate the
mandible for closure. It is not a power muscle. In addition
contraction of the middle and posterior portions of the
temporalis muscle can contribute to retrusive movements of
the mandible. To a small degree unilateral contraction of the
temporalis assists in deviation of the mandible to the ipsilateral
side.
43

 The masseter muscle, a short rectangular muscle taking its origin from
the zygomatic arch and inserting on the lateral surface of the mandible, is
the most powerful elevator of the mandible and functions to create
pressure on the teeth, particularly the molars, in chewing motions.
 The masseter muscle is composed of two portions, superficial and deep,
which are incompletely divided, yet have somewhat different functions.
The superficial portion originates from the lower border of the zygomatic
bone and the anterior two-thirds of the zygomatic arch and passes
inferiorly and posteriorly to insert on the angle of the mandible.
 The deep head originates from the inner surface of the entire zygomatic
arch and on the posterior one-third of the arch from its lower border. The
deep fibers pass vertically to insert on the mandible on its lateral aspect
above the insertion of the superficial head.
44

 The superficial portion in particular has a multipennate appearance with
alternating tendinous plates and fleshy bundles of muscle fibers, which
serve to increase the power of the muscle.
 Both the superficial and deep portions of the masseter muscle are
powerful elevators of the mandible, but they function independently and
reciprocally in other movements.
 Electromyographic studies show that the deep layer of the masseter is
always silent during protrusive movements and always active during
forced retrusion, whereas the superficial portion is active during
protrusion and silent during retrusion.
 Similarly the deep masseter is active in ipsilateral movements but
does not function in contralateral movements, whereas the superficial
masseter is active during contralateral movements but not in
ipsilateral movements.
45

A, Masseter muscle. SP, superficial portion; DP, deep portion.
B, Function: elevation of the mandible.
46

The medial pterygoid muscle is rectangular and takes its
origin from the pterygoid fossa and the internal surface of the
lateral plate of the pterygoid process, with some fibers arising
from the tuberosity of the maxilla and the palatine bone. Its
fibers pass inferiorly and insert on the medial surface of the
mandible, inferiorly and posteriorly to the lingual.
Like the masseter muscle the medial pterygoid fibers have
alternating layers of fleshy and tendinous parts, thereby
increasing the power of the muscle. The main function of the
medial pterygoid is elevation of the mandible, but it also
functions somewhat in unilateral protrusion in a synergism with
the lateral pterygoid to promote rotation to the opposite side.
47

A, Medial pterygoid muscle.
B, Function: elevation of the mandible.
48

The lateral pterygoid muscle has two portions that can be
considered two functionally distinct muscles. The larger inferior
head originates from the lateral surface of the lateral pterygoid
plate. Its fibers pass superiorly and outward to fuse with the
fibers of the superior head at the neck of the mandibular
condyle, inserting into the pterygoid fovea.
The superior head originates from the infratemporal surface of
the greater sphenoid wing, and its fibers pass inferiorly,
posteriorly, and outward to insert in the superior aspect of the
pterygoid fovea, the articular capsule, and the articular disk at
its medial aspect, as well as to the medial pole of the condyle.
Anatomic studies have shown that the majority of the superior
head fibers insert into the condyle rather than the disk.
49

The inferior and superior heads of the lateral pterygoid muscle
function independently and reciprocally. The primary function of
the inferior head is protrusive and contralateral movement.
When the bilateral inferior heads function together, the condyle
is pulled forward down the articular eminence, with the disk
moving passively with the condylar head.
This forward movement of the condyle down the inclined plane
of the articular eminence also contributes to opening of the oral
cavity. When the inferior head functions unilaterally the
resulting medial and protrusive movement of the condyle
results in contralateral motion of the mandible. The function of
the superior head of the lateral pterygoid muscle is
predominantly involved with closing movements of the jaw and
with retrusion and ipsilateral movement.
50

A, Inferior and superior lateral pterygoid muscles.
B, Function of the inferior lateral pterygoid: protrusion of
the mandible. 51

INFRAMANDIBULAR MUSCLE
GROUP
 The inframandibular muscles can be subdivided into two groups: the
suprahyoids and the infrahyoids. The suprahyoid group consists of the
digastric, geniohyoid,mylohyoid, and stylohyoid muscles; lies between
the mandible and the hyoid bone; and serves to either raise the hyoid
bone, if the mandible is fixed in position by the supramandibular group,
or depress the mandible, if the hyoid bone is fixed in position by the
infrahyoids.
 The infrahyoid group, consisting of the sternohyoid, omohyoid,
sternothyroid, and thyrohyoid muscles, attaches to the hyoid bone
superiorly and to the sternum, clavicle, and scapula inferiorly. This
group of muscles can either depress the hyoid bone or hold the hyoid
bone in position, relative to the trunk, during opening movements of the
mandible.
53

Movement of the head
and neck is a result of
the finely coordinated
efforts of many
muscles.
The muscles of
mastication represent
only part of this
complex system.
55

BIOMECHANICS OF TEMPOROMANDIBULAR
JOINT MOVEMENT
 Complex free movements of the mandible are made possible by the relation of four distinct
joints that are involved in mandibular movement: the inferior and superior joints—
bilaterally. Two types of movement are possible: rotation and translation.
 The inferior joints, consisting of the condyle and disk, are responsible for rotation, a hinge-
like motion. The center of rotation is considered to be along a horizontal axis passing
through both condyles.
 In theory pure hinge motion of approximately 2.5 cm measured at the incisal edges of the
anterior teeth is possible.
 Nevertheless most mandibular movements are translatory as well, involving a gliding
motion between the disk and the temporal fossa, which are the components of the
superior joints.
 The mandible and disk glide together as a unit because they are held together by the
collateral ligaments. The maximum forward and lateral movement of the upper joint in
translation is approximately 1.5 cm.
56

All movements of the mandible, whether symmetric or
asymmetric, involve close contact of the condyle,
disk, and articular eminence. Pure opening, closing,
protrusive, and retrusive movements are possible as
a result of bilaterally symmetric action of the
musculature.
Asymmetric movements, such as those seen in
chewing, are made possible by unilateral movements
of the musculature with different amounts of
translation and rotation occurring within the joints on
either side.
57

Normal movement of the condyle and disc
during mouth opening.
As the condyle moves out of the fossa, the disc
rotates posteriorly on the condyle.
Rotational movement occurs predominantly in
the lower joint space while translation occurs
predominantly in the superior joint space.
58

The positioning of the condyle and disk within the fossa, as
well as the constant contact between the condyle, disk, and
eminence, is maintained by continuous activity of the
muscles of mastication, particularly the supramandibular
group.
The ligaments associated with the TMJ do not move the joint.
Although they can be lengthened by movements of muscles,
they do not stretch (ie, do not have an elastic recoil that
returns them to a resting position automatically).
59

Instead the role of the ligaments is that of a passive
restriction of movement at the extreme ranges of
motion. During normal function rotational and
translational movements occur simultaneously,
permitting the free range of motion necessary in
speaking and chewing.
60

Normal functional
movement of the
condyle and disc
during the full range
of opening and
closing.
The disc is rotated
posteriorly on the
condyle as the
condyle is translated
out of the fossa.
The closing
movement is the
exact opposite of
opening.
61

EVALUATION
The evaluation of the patient with temporomandibular
pain, dysfunction, or both is like that in any other
diagnostic work up.
This evaluation should include a thorough history, a
physical examination of the masticatory system, and
problem-focused TMJ radiography.
62

INTERVIEW
 The patient's history may be the most important part of the evaluation
because it furnishes clues for the diagnosis. The history begins with the
chief complaint, which is a statement of the patient's reasons for
seeking consultation or treatment.
 The history of the present illness should be comprehensive, including
an accurate description of the patient's symptoms, chronology of the
symptoms, description of how the problem affects the patient and
information about any previous treatments (including the patient's
response to those treatments).
 To have patients complete a general questionnaire is often useful to
help provide information about the history of their problem. The use of a
visual analog pain scale may also help obtain an under· standing of the
patient's perception of the severity of their pain. 63

EXAMINATION
The physical examination consists of an evaluation of the
entire masticatory system. The head and neck should be
inspected for soft tissue asymmetry or evidence of muscular
hypertrophy.
The patient should be observed for signs of jaw clenching or
other habits. The masticatory muscles should be examined
systematically. The muscles should be palpated for the
presence of tenderness, fasciculations, spasm, or trigger
points.
64

Systematic evaluation of muscles of
mastication.
A, Palpation of masseter muscle.
B, Palpation of temporalis muscle.
C, Palpation of temporalis tendon attachment on
coronoid process and ascending ramus.
65

The TMJs are examined for tenderness and noise. The location
of the joint tenderness (e.g., lateral or posterior) should be
noted. If the joint is more painful during different areas of the
opening cycle or with different types of functions, this should be
recorded.
The most common forms of joint noise are clicking (a distinct
sound) and crepitus (i.e., scraping or grating sounds). Many
joint sounds can be easily heard without special
instrumentation or can be felt during palpation of the joint;
however, in some cases auscultation with a stethoscope may
allow less obvious joint sounds, such as mild crepitus, to be
appreciated.
66

Evaluation or temporomandibular joint for
tenderness and noise. Joint is palpated laterally
in closed position (A) and open position (B).
67

The mandibular range of motion should be determined. Normal
range of movement of an adult's mandible is about 45 mm
vertically (i.e., interincisally) and 10 mm protrusively and
laterally.
The normal movement is straight and symmetric. In some
cases, tenderness in the joint or muscle areas may prevent
opening. The clinician should attempt to ascertain not only the
painless voluntary opening but also the maximum opening that
can be achieved with gentle digital pressure.
In some cases the patient may appear to have a mechanical
obstruction in the joint causing limited opening but with gentle
pressure may actually be able to achieve near normal opening.
This may suggest muscular rather than intracapsular problems.
68

Measurement of range
of jaw motion.
A, Maximum voluntary
vertical opening.
B, Evaluation or lateral
excursive movement
(should be
approximately 10 mm).
Protrusive movements
should be similar to
excursion.
69

 The dental evaluation is also important. Odontogenic sources of pain
should be eliminated. The teeth should be examined for wear facets,
soreness, and mobility, which may be evidence of bruxism.
 Although the Significance of occlusal abnormalities is controversial, the
occlusal relationship should be evaluated and documented. Missing teeth
should be noted, and dental and skeletal classification should be
determined.
 The clinician should note any centric relation and centric occlusion
discrepancy or Significant posturing by the patient. The examination
findings can be summarized on a TMD evaluation form and included in
the patient's chart. In many cases a more detailed chart note may be
necessary to document adequately all of the history and examination
findings described previously.
70

RADIOGRAPHIC
EVALUATION
Radiographs of the TMJ are helpful in the diagnosis of
intraarticular, osseous, and soft tissue pathologic conditions.
The use of radiographs in the evaluation of the patient with
TMD should be based on the patient's signs and symptoms
instead of routinely ordering a standard set of radiographs. In
many cases the panoramic radiograph provides adequate
information as a screening radiograph in evaluation of TMD.
A variety of other radiographic techniques are available that
may provide useful information in certain cases.
71

PANORAMIC RADIOGRAPHY
 One of the best overall radiographs for screening evaluation of the
TMJs is the panoramic radiograph. This technique allows visualization
of both TMJs on the same film.
 Because a panoramic technique provides a tomographic-type view of
the TMJ , this can frequently provide a good assessment of the bony
anatomy of the articulating surfaces of the mandibular condyle and
glenoid fossa; and other areas, such as the coronoid process, can also
be visualized.
 Many machines are equipped to provide special views of the mandible,
focusing primarily on the area of the TMJs. These radiographs can
often be complete in the open and closed position.
72

Panoramic imaging. A, Normal anatomy or right condyle. B, Imaging
illustrates degenerative changes or left condyle via remodeling.
73

TOMOGRAMS
The tomographic technique allows a more detailed
view of the TMJ. This technique allows radiographic
sectioning of the joint at different levels of the condyle
and fossa complex, which provides individual views
visualizing the joint in "slices" from the medial to the
lateral pole. These views eliminate bony
superimposition and overlap and provide a relatively
clear picture of the bony anatomy of the joint.
74

TEMPOROMANDIBULAR
JOINT ARTHROGRAPHY
 This imaging method was the first technique available that allowed
visualization (indirect) of the intra articular disk. Arthrography involves
the injection of contrast material into the inferior or superior spaces of a
joint, after which the joint is radiographed.
 Evaluation of the configuration of the dye in the joint spaces allows
evaluation of the position and morphology of the articular disk.
 This technique also demonstrates the presence of perforations and
adhesions of the disk or its attachments. With the availability of more
advanced, less invasive techniques, arthrography is rarely used.
75

Arthrogram shows dye in inferior and superior joint spaces. Anatomy and location of
disk is indirectly interpreted from dye pattern observed after injection of joint spaces
above and below disk. This arthrogram demonstrates anterior disk displacement
without reduction. A, Closed position. B, Open position.
76

COMPUTED TOMOGRAPHY
 Computed tomography (CT) provides a combination of tomographic
views of the joint, combined with computer enhancement of hard and
soft tissue images. This technique allows evaluation of a variety of hard
and soft tissue pathologic conditions in the joint. CT images provide the
most accurate radiographic assessment of the bony components of the
joint.
 CT scan reconstruction capabilities allow images obtained in one plane
of space to be reconstructed so that the images can be evaluated from
a different view. Thus evaluation of the joint from a variety of
perspectives can be made from a single radiation exposure.
77

Computerized tomography.
A , Coronal images illustrate
normal architecture of the right
(R) condyle with alteration
of the left condyle resulting
from a history of trauma.
B, Axial views depict the altered
condylar anatomy referenced
against the contralateral joint.
78

MAGNETIC RESONANCE
IMAGING
The most effective diagnostic imaging technique to evaluate
TMJ soft tissues is magnetic resonance imaging.
This technique allows excellent images of intra articular soft
tissue, making MRI a valuable technique for evaluating disk
morphology and position.
MRI images can be obtained showing dynamic joint function
in a cinematic fashion, providing valuable information about
the anatomic components of the joint during function. The
fact that this technique does not use ionizing radiation is a
significant advantage.
79

Magnetic resonance image. A, Normal positioning of the articular disk between the
articular eminence and condyle during translation. B, Image demonstrates anterior
disk displacement without reduction, limiting range of motion.
80

NUCLEAR IMAGING
 Nuclear medicine studies involve intravenous injection of technetium-
99, a y-emitting isotope that is concentrated in areas of active bone
metabolism. Approximately 3 hours after injection of the isotope,
images are obtained using a gamma camera. Single-photon emission
computerized tomography images can then be used to determine active
areas of bone metabolism.
 Although this technique is extremely sensitive, the information obtained
may be difficult to interpret. Because bone changes, such as
degeneration, may appear identical to repair or regeneration, this
technique must be evaluated cautiously and in combination with clinical
findings.
81

Single-photon emission
computed tomography (bone
scan). Area of increased
activity is apparent in both
temporomandibular
joints.
82

PSYCHOLOGICAL
EVALUATION
 Many patients with temporomandibular pain and dysfunction of long-
standing duration develop manifestations of chronic pain syndrome
behavior.
 This complex may include gross exaggeration of symptoms and clinical
depression. The comorbidity of psychiatric illness and
temporomandibular dysfunction can be as high as 10% to 20% of
patients seeking treatment
 A third of these patients is suffering from depression at the time on
initial presentation, whereas more than two thirds have had a severe
depressive episode in their history.
83

Psychiatric disorders may elicit somatic components through
parafunctional habits resulting in dystonia and myalgia, and
individuals with chronic pain commonly have a higher
incidence of concomitant anxiety disorders.
Behavioral changes associated with pain and dysfunction can
be elicited in the history through questions regarding functional
limitation that results from the patient's symptoms.
If the functional limitation appears to be excessive compared
with the patient's clinical signs or the patient appears to be
clinically depressed, further psychological evaluation may be
warranted.
84

Lecture 9 TMJ anatomy examination

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