Temporomandibular joint or craniomandibular joint is a form of articulation found
only in mammals. This is called as Temporomandibular joint because this joint is formed
by the articulation of mandibular condyle at the base of the cranium with the squamous
part of temporal bone.
Also known as craniomandibular joint as the mandible is connected to the
cranium through this joint. Temporomandibular is by far the most complex joint in the
As it provides hinging movement in one plane (ie) forward and backward like
hinge of a door it is called as ginglymoid joint. However, at the same time it also provides
gliding movement which classifies it as an arthrodial joint so known as ginglymoarthodial
It is known as a modified ball socket type of joint as it allows movements in three
planes, sagittal, transverse and coronal. It is also known as compound joint. Compound
joint is the joint formed by these articulations of three bones. As the articular disc
functionally serves as a non-ossified bone that permits the complex movements of the
joints, the joint are called even as a compound joint.
The physiologic activities in which the temporomandibular joint plays a part may
be voluntary or reflex and ranges from mastication, deglutition and phonation, to such
momentary actions such as grasping and yawning.
Development of Temporomandibular Joint
The mammalian craniomandibular articulation develops anterolateral to the otic
capsule from the first branchial arch mesenchyme and is therefore innervated by fifth
cranial nerve. This is the early embryonic joint.
This primary embryonic joint is formed by the joining or is the joint between
malleus and incus which develops from first branchial arch. The malleus and incus are
formed by differentiation of large islands of cartilage, found in the middle ear cavity. This
joint serves as the primary TMJ joint up to 16 weeks of prenatal life. This joint is an
uniaxial hinge joint capable of no lateral motion.
By the end of 7-11 weeks of gestation the secondary TMJ begins to develop. At
about ninth prenatal week a condensation of mesenchyme appears surrounding the
upper posterior surface of rudimentary ramus.
This mass chondrifies at about 10-11 weeks to form cartilaginous mandibular
condyle. With progressive endochondral ossification the cartilage fuses with the posterior
part of the bony mandibular body. At about 9-10 weeks the muscle fibers become more
differentiated Bloodvessels, nerves etc. can be seen clearly present in the joint region at
about 10 weeks of gestation.
The appearance of mandibular fossa of the temporal bone is some what earlier
than that of the condyle (u) at about 7-8 weeks. Ossification of the fossa is more
prominent at about 10-11 weeks. Ossification continuous in this region and at about 22
weeks the mandibular fossa shows both medial and lateral walls and articular eminence
is evident. The shape of the fossa is concave at about the ninth week and it takes the
definitive concave shape to match the convex condyle. The differentiating mesenchymal
cells interposed between the condyle and mandibular fossa gives rise to the capsular
and intracapsular structures of the TM joints.
Articular disc is first seen at about seven and one half weeks. By the 10th
first signs of collagenous fibers within the articular disc develop and it becomes more
pronounced by 12 weeks. From the 19-20th
week the disc increasingly takes on its
definitive fibro cartilaginous composition. At this stage only the disc shows pattern of
differential cell proliferation in which central region becomes thinner than periphery.
The articular capsule first appears at about 9-11 weeks. By the 17th
capsule is seen as fully formed tissue boundary between intracapsular and extracapsular
components of the TMJ. By the 13th
week the lower cavity of the fossa enlarges and the
superior joint cavity becomes more evident. The shapes of the joint cavities are
reciprocal at the time when the upper joint cavity is concave the lower joint cavity is
Works done by Hooker (1954 and Humphrey (1968) shows that actual mouth
opening actions are observable as early as 7-8 weeks of gestation.
But certain others like Symons (1952), Perry (1985), Moffet (1957) said that only
scattered muscle fibers of lateral pterygoid muscle are clearly discernible at 7-8 weeks.
Therefore, the prenatal jaw opening activity that both Hooker and Humphery observed is
said to have involved the articulations of the primary TMJ.
Anatomy of the TMJ
The temperomandibular joint or craniomandibular articulation is the articulation
between the lower jaw and the cranium. The bony elements of this joint are the
squamous part of the temporal bone above and the mandibular condyles below. This
articulation consists of two synovial joints, the left and right temporomandibular joint.
TMJ is complex both morphologically and functionally. An articular disc
composed of dense fibrous tissue is interposed between the temporal bone and the
mandible dividing the articular space into an upper and lower compartment, gliding
movement occurs in upper compartment and the lower compartment functions as a
hinge joint. The articulating surface of the TMJ are lined by dense, avascular fibrous
Relations of TMJ
Laterally 1) Skin, Fasciae.
2) Parotid gland.
3) Temporal branches of the VII nerve.
Medially Tympanic plate separates TMJ from internal carotid artery,
spine of the sphenoid with upper end of sphernomandibular
ligament, Auriculotemporal and chorda tympani. Middle
Anteriorly Lateral pterygoid muscles.
Massetric nerve and vessels.
Posteriorly The parotid gland separates it from external acoustinc
Superiorly Middle cranial fossa
Middle meningel vessels.
Inferiorly Maxillary artery and vein
Blood supply Superficial temporal artery and maxillary artery
Nerve supply Aurientotemporal nerve and massetered nerve.
FUNCTIONAL ANATOMY OF THE TMJ
This is convex in shape and it articulates with the articular fossa which is
separated into the upper and lower compartments by the articular disc. it present as an
ovoid bony knob like process on a narrow mandibular neck. The adult condyle is about
15-20mm mediolaterally and 8-10mms anterio-posteriorly. The articular surface of the
condyle faces upwards and forwards so that in side view the neck of the condyloid
process seems to bend forward. The lateral pole of the condyle extends slightly beyond
the ramus and is roughened for the attachment of articular disc and temporomandibular
Each human TMJ is essentially a double joint due to the presence of an intra
The articular surface are of fibrous tissue, condylar perichondrum and temporal
periosteum. Technically classified as a ginglymo arthrodial joint. It adjusts itself to the
changing contours of the condyle head as it moves in the fossa. This is possible as the
disc is not uniformly thick, but is modified in different regions. The underside of the disc
is concave and fits closely over the condylar head like a cap. This ensures the rotatory
movements of the condylar head in the fossa and the disc moves along with the condyle.
In sagittal section, the disc is divided into three regions according to thickness.
The central area is the thinnest and is called intermediated zone. In a normal condyle is
located In the intermediate zone of the disc, bordered by thicker anterior and
posterior regions. From anterior to posterior the disc shows five zones :
1) Anterior extension
2) Anterior band
3) Intermediate zone
4) Posterior extension
5) Posterior band
Posteriorly the disc is bilaminar. The thickened anterior and posterior bands
forms an ellipsoidal doughnut. This ellipsoidal doughnut functions to stabilize the
condylar head in the glenoid fossa with the jaws at rest. The disc is thus considered as a
flexible, viscoelastic adapter which helps the moving joint surface achieve more off
effective articular surface congruity.
This is the concavity within the temporal bone that houses the mandibular
condyle. The anterior wall of the fossa is formed by articular eminence and posterior
wall is formed by the tympanic plate.
The fossa is lined by articular tissue. The posterior part of the fossa elevated to
a ridges called the posterior articular lip.
The posterior articular lip is higher and thicker at its lateral end and is known as
post glenoid process. Medially the articular fossa is bounded by a bony plate that
leans against the spine of sphenoid sometimes drawn into a triangular process
and is known as the temporal spine.
The capsule forms a thin, fibrous connective tissue sleeve about the joint
which tapers from above down to the condyle neck. It is attached to squamous
temporal bone just peripheral to the margins of the articulating surfaces. They are
vertically oriented and are of such a length so as enable the normal range of joint
movements. All the non articulating surface within the capsule form sunovial membrane,
the surface area of which is increased by the formulation of villi and folds. The sinovial
fluid is a dialysate of plasma with added, mucins and proteins. The cells it contains are
mainly lymphoid or macrophage in type. The thickened anterolateral and lateral
portions of the capsule which is attached to the articular tubercles is called
Ligaments of temperomandibular joint
Ligaments limit the movements of temperomandibular joint. The capsule is too
delicate a structure to support the joint unaided and so joint stability is achieved with
intrinsic and extrinsic ligaments.
Intrinsic ligaments (directly involved with movement of joint and attached in
relation to joint).
The main intrinsic ligament is the temperomandibular ligament or the lateral
ligament. It is located lateral to the capsule. The fibers of the ligament pass obliquely
from its wide origin lateral to the articular tubercle to a narrow insertion in the neck of the
condyle, below and behind the lateral pole of the condyle. Collateral ligaments also act
as intrinsic ligaments. These are rather narrow bands of collagen fibers that run
horizontally backwards on the inner aspect of the capsule from the lateral and medial
aspects of the articular eminence to the respective condyle poles. These restrict the
distal displacement of condyle head. These collateral ligaments along with the
temperomandibular ligaments, helps to attain the clinical ligamentous position.
These are not directly involved with the joint, but they modify the range of
movements that are possible.
These are also known as accesory ligaments and they include -
1) Sphenomandibular ligament
2) Stylo mandibular ligament
3) Pterygomandibular raphe
4) Temporomandibular ligament of the opposite side which acts as an extrinsic
Attached superiorly to the spine of the sphenoid and inferiorly it is attached to
the lingula of the mandibular foramen. It is a remnant of the cephalic end of
It is attached above to the lateral surface of styloid process and below to the
angle and posterior border of the ramus of the mandible.
Fibrous capsule and articular disc also serves as the ligaments of TM joint.
Muscles of mastication
Origin Insertion Action
Masseter a) Superficial layer from
borer of zygomatic arch
and adjoining zygomatic
process of maxilla.
Lower part of lateral
surface of the ramus
of the mandible
Elevation of mandible.
b) Middle layer anterior
2/3 of deep surface and
posterior 1/3 of lower
border of zygomated
Middle part of ramus
Deeplayer (origin) Insertion
From deep layer of zygomated
With the upper part of ramus and
1) Temporal fossa
excluding zygomatic bone
2) Temporal fascia
Margins and deep surface of coronoid
Anterior border of ramus of mandible
1. Elevates mandible
2. Posterior fibers retrat the protruded mandible
3. Helps in side to grinding movements.
Lateral pterygoid origin Insertion
1. Upperhead from infra temporal
surface and crest of greater wing
Pterygoid fovea on the anterior surface of
the neck of the mandible.
2. Lower head from lateral surface of
lateral pterygoid plate.
Anterior margin of articular disc and
capsule of temporomandibular joint.
1. With the help of suprahyoid muscles helps in depressing mandible to open the
2. Helps in protruding mandible along with medial pterygoid.
3. With medial pterygoid of the same side and alternating with those of the opposite
side brings about side to side grinding movements.
Medial pterygoid Origin Insertion
1. Superficial head
2. Deep head from medial surface of
lateral pterygoid plate and
adjoining process of palatine bone.
Roughened area on the medial surface of
angle and adjoining ramus of mandible,
below and behind the mandibular foramen
and mylohyoid groove.
1. Elevates mandible
2. Helps to protrude mandible
3. Brings about side to side grinding movements along with lateral pterygoid.
Movement of the mandible
Both joints always act together, but may differ In movement which include
gliding, spinroll and angulation. The basic movements that occur in TM joint are
rotatory and translatory. Rotatory movements occur in the lower chamber and
translatory movements occur in upper chamber. These movements occur
symmetrically in both joints, when mandible is raised lowered protruded or retruded.
Movements also occur in asymmetrical manner when translation occurs on
one side only to produce lateral jaw positions.
Various movements of the TMJ according to the movement of mandible are -
5) Lateral chewing movemente and bonnet movement.
Depression of mandibular opening
The opening movement is caused by gravity, relaxation of the elevator
muscles and a combined action of lateral pterygoid, ganiohyoid, mylohyoid and
digastric muscles. Condyles rotate on a common horizontal axis and also glide
forwards and downwards, on the interior surface of the articular disc which slides in
the same direction on the temporal bones due to their attachments to the
mandibular heads and due to the contraction of lateral pterygoide which draw the heads
and discs onto the articular tubercle.
When wide opening occurs the protracting force of the inferior heads of the
lateral pterygoid muscles acting upon the condyles and the disc combines with the
depressing and retracting force of the geniohyoid and degastric muscles acting upon
the chin and action of mylohyoid muscle on the body of the mandible. These
combined forces produce extensive rotatory and translatory movements.
Elevation or closing movements of the mandible
Closing movement is executed by the elevators of the mandible. Condyles glides
backwards and hinges on its disc and as lateral pterygoid relaxes the disc glides back
and up into the mandibular fossa.
The muscles involved are the temporalis, masetter, and medial ptarygoid of both the
sides. The condyles are retracted by posterior fibers of temporalis during closure. The
disc is pulled backwards by the bilammiar elastic tissue.
In protrusive movements the lower teeth are drawn forward over the upper teeth.
This is primarily as a result of contraction of inferior heads of lateral pterygoid
muscles although there is slight activity of the masseter and medial pterygoid muscles.
The condyle is pulled forward and downward along the articular eminences
while the elevators and depressors apparently stabilize the position of the mandible
related to maxilla.
RETRACTION Of THE MANDIBLE
In this movement the obliquely aligned fibers of the middle temporalis muscle
combine forces with the depressors while the remaining elevators exhibit varying
amount of activity. The articular disc and condyles are pulled backwards into the
mandibular fossa by the contraction of the posterior fibers of temporal is. deep fibers
of the masseter and geniohyoid and digastric play a minor role.
Retrusion is limited to a distance of 1 mm.
Lateral chewing movement
One head with its articular disc glides forwards rotating around a vertical axis
immediately behind the opposite head, then slides backward rotating on the opposite
direction, as the opposite head comes forward In turn. This alternation swings mandible
from side to side muscles involved are medial and lateral pterygoids of each side acting
Definition : The bodily lateral movement or lateral shift of the mandible resulting from
the movements of the condyles along the lateral inclines of the mandibular fossa in
lateral jaw movements.
Bennet angle - The angle formed by the sagittal plane and the path of the advancing
condyle during lateral mandibular movements as viewed in the horizontal plane.
When the mandible moves to one side or the other either in opening or closing
the condyle on the side to which the mandible is moving rotates minimally and
moves forwards downwards and laterally. For example the mandible moves to the
right, the left condyla moves downwards, forwards and inwards while in contact with
meniscus and eminence. The right condyla is allowed only a small rotatory movement,
because its lateral pole is limited by the temperomandibular ligament and cannot move
backwards for more than 1 mm. It therefore moves laterally and slightly forwards and
downwards due to the combined action of the left lateral and medial pterygoid and to
the contacts that exists between the condyles, menisci and fossa. The force causing the
movement comes from the left side and right condyles moves as it can within the limits
of its ligaments.
Bennet movement consists of an immediate translation which takes place
before the rotation and a progressive translation which accompanies rotation.
CONTROL OF TMJ MOVEMENTS
The muscle which move the TMJ like the muscles found anywhere In the
body are subject to both reflex controls and controls arising from within the central
nervous system. There are three principal reflexes which control the vertical
relationship between the mandible and maxilla and hence TMJ movements. These are
as follows :
1) Jaw jerk reflexes
2) Jaw opening reflexes
3) Jaw unloading reflexes.
Jaw Jerk Reflexes
The jaw jerk is analogous to the knee jerk and is a stretch reflex whereby
stretching the jaw closing muscles (u) usually by applying a downward tap on the
chin produces a reflex contraction of these muscles. This demonstrates that there is
feedback mechanism from jaw closing muscles to their own motor neurons in the central
nervous system, as one rarely receives downward blows on the chin. This feedback
loop comes from muscle spindles within the muscles which through their primary
afferent nerves make direct connections with the motorneurones in the trigeminal motor
muscles. This feedback mechanism helps with the fine control of TMJ movements
throughout normal function, like taking account of different consistencies of food.
There is no such mechanism for the jaw opening muscles as they contact few or
no muscle spindles.
Jaw opening reflex
These are effected by inhibition of activity in jaw closing muscles, but do not
show any activation of jaw opening muscles. This reflex can be triggered by
stimulating mechanoreceptive nerves from most structures within the mouth or
nociceptive nerves from the mouth or face. The pathway for jaw opening reflex is
polysynaptic with the first synapse in either the trigeminal sensory nuclei or the
adjacent reticular formation and the final one in the trigeminal motor nucleus. The
importance of these reflexes probably lies in their ability to prevent injury when biting or
liable to produce damage.
Jaw Unloading Reflex
This reflex also involves a cessation of activity in jaw closing muscles, together
with an activation of opening muscles.
This reflex is evoked when a hard object which is being bitten breaks suddenly,
thus unloading the jaw closing muscles of the resistance against which they were
working. The result of which is that opposing teeth do not forcibly hit into one another,
thereby preventing damage. The explanation for this is as follows. When biting on an
object which one knows or suspects might be brittle, one sends exatatory signals
not only to the jaw closing motor neurons but also as a precaution to those of the jaw
The jaw closing motor neurons also receive positive feedback from their own
muscle spindles and there may be negative feedback to the jaw opener motor
neurones from this same source. This is called as reciprocal inhibition.
When the object breaks the sudden shortening of the muscle would result in
a decrease in spindle activity and hence in the overall excitatory drive to the jaw
closing muscles as well as in a disinhibition of the jaw opening motor neurones. Thus
the decreases and increases in activity in the jaw closing and opening muscles
respectively would be produced.
In addition to the vertical jaw reflexes there are also horizontal jaw reflexes
which involve lateral, protrusive, and may be retrusive movements of the jaw in
response to stimulation of mechanoreceptors in the periodontium and oral mucosa
and TMJ. These may be of great significance in the function and dysfunction of the
TMJ as this may be superimposed upon the normal chewing pattern.
1. Anatomy Of Head And Neck
2. Applied Physiology Of Mouth
- Lave I ie
3. Functional Anatomy Of Oral Tissues
- Shaw J. H.
4. The Structure And Function Of Temperomandibular Joint
- G. S. Mackay, R. Yemm.