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Temporomandibular Joint: Review of the Anatomy, Pathology, and Magnetic Resonance Imaging…
101
of contrast agents, making it a comfortable
option for patients [5, 10, 11].
3.1.2 Limitations
1. Cost: MRI is an expensive imaging modality
compared to conventional radiographs or CT
scans, making it less accessible in some
healthcare settings.
2. Time-consuming: MRI scans can take longer
than conventional radiographs or CT scans,
which can be a limiting factor in emergency
situations.
3. Claustrophobia: Some patients may experience claustrophobia during MRI scans, which
can limit the use of this imaging modality in
some patients.
4. Metallic implants: Patients with metallic
implants, such as dental implants or pacemakers, may not be eligible for MRI scans due to
safety concerns [8, 10, 11].
3.2 Current Advancements inMRI
forTMJ Injury Evaluation
Advancements in MRI technology have improved
the accuracy and efciency of TMJ injury evaluation. One such advancement is the use of highresolution MRI, which provides detailed images
of the TMJ structures, including the articular disc,
ligaments, and muscles. High-resolution MRI is
particularly useful in the evaluation of small or
subtle injuries, which may be missed on conventional MRI scans. Another advancement is the use
of functional MRI (fMRI), which can provide
information on the functional status of the TMJ.
fMRI can evaluate the TMJ during active mouth
opening and closing, providing information on
the movement patterns and muscle activation during these movements. This information can be
useful in the assessment of TMJ dysfunction and
in the planning of TMJ surgeries [26, 27].
3.2.1 TMJ Dislocation
TMJ dislocation occurs when the mandible
(lower jawbone) becomes dislocated from the
temporal bone (skull bone) that forms the joint.
This can occur due to a variety of factors, includ-
ing trauma, overuse, or underlying structural
abnormalities. The symptoms of TMJ dislocation
can range from mild discomfort to severe pain
and functional impairment [18, 20, 21].
MRI can be a valuable tool for evaluating TMJ
dislocation, as it provides detailed images of the
joint and surrounding structures. These images can
help healthcare professionals identify the underlying causes of the dislocation, as well as any structural abnormalities or damage to the joint that may
be contributing to the problem [22, 23, 28].
3.2.2 Causes ofTMJ Dislocation
TMJ dislocation can occur due to a variety of factors, including trauma, overuse, or underlying
structural abnormalities.
Trauma: Trauma to the jaw or head can cause
the mandibular condyle to become dislocated
from the temporal bone. This can occur due to a
blow to the face, a fall, or a car accident, among
other things.
Overuse: Overuse of the TMJ can also lead to
dislocation. This can occur due to excessive
chewing or grinding of the teeth, or as a result of
certain habits such as nail biting or clenching the
jaw [18, 22, 23].
Structural abnormalities: Underlying structural abnormalities can also contribute to TMJ
dislocation. These can include deformities of the
mandibular condyle or temporal bone, as well as
abnormalities of the articular disc or joint capsule
[29].
Symptoms
The symptoms of TMJ dislocation can vary
depending on the severity and underlying cause
of the problem. Some common symptoms include
[23, 27, 30]:
1. Pain or discomfort in the jaw joint or sur-
rounding areas
2. Limited range of motion or difculty opening
and closing the mouth
3. Clicking, popping, or grating sounds when
moving the jaw
4. Locking of the jaw in an open or closed
position
5. Headaches
102
F. A. Chagas-Neto et al.
3.2.3 TMJ Fractures
Temporomandibular joint (TMJ) fractures are
relatively uncommon but can be a signicant
source of pain and dysfunction. They can occur
due to a variety of factors, including trauma,
overuse, or underlying structural abnormalities.
Magnetic resonance imaging (MRI) is a noninvasive diagnostic tool that can be used to evaluate
TMJ fractures and aid in treatment planning [26].
Trauma: Trauma to the jaw or head can cause
fractures to the mandibular condyle or other
structures of the TMJ.This can occur due to a
blow to the face, a fall, or a car accident, among
other things.
Overuse: Overuse of the TMJ can also lead to
fractures. This can occur due to excessive chewing or grinding of the teeth, or because of certain
habits such as nail biting or clenching the jaw.
Structural abnormalities: Underlying structural abnormalities can also contribute to TMJ
fractures. These can include deformities of the
mandibular condyle or temporal bone, as well as
abnormalities of the articular disc or joint capsule
[27, 31].
Symptoms
The symptoms of TMJ fractures can vary depending on the severity and underlying cause of the
problem. Some common symptoms include [27,
30]:
1. Pain or discomfort in the jaw joint or sur-
rounding areas
2. Swelling or tenderness around the TMJ
3. Limited range of motion or difculty opening
and closing the mouth
4. Clicking, popping, or grating sounds when
moving the jaw
5. Locking of the jaw in an open or closed
position
3.2.4 MRI intheEvaluation ofTMJ
Fractures
MRI can be a valuable tool for evaluating TMJ
fractures, as it provides detailed images of the
joint and surrounding structures. These images
can help healthcare professionals identify the
location and extent of the fracture, as well as any
associated soft tissue injuries. MRI can also help
differentiate TMJ fractures from other causes of
jaw pain and dysfunction, such as arthritis or
muscle strain [26, 31].
4 Internal Derangements
andDegeneration
Internal derangement (ID) refers to a joint malfunction that disrupts smooth joint function,
caused by abnormal interaction of the articular
disc, condyle, and articular eminence. Clinical
features of ID include articular pain and noises.
The most common cause of ID is disc displacement, but not all displaced discs are associated
with derangement, and not all derangements are
caused by disc displacement. Loose bodies, joint
effusion, and adhesions in the joint can also cause
derangement. Surprisingly, up to 34% of asymptomatic volunteers may have anterior disc displacement, and 23% of patients with derangement
may have normal disc position [32–34].
Approximately 80% of patients referred for
diagnostic imaging of the TMJ demonstrate some
form of disc displacement in most large MRI
series. MRI is the preferred imaging method for
diagnosing ID, with a 95% accuracy rate for
assessing the disc position and shape, and a 93%
accuracy rate for assessing osseous changes
[33–35].
4.1 Temporomandibular Joint
Developmental Disorders
Temporomandibular joint (TMJ) developmental
disorders are a group of conditions that affect the
growth and function of the TMJ.The TMJ is the
joint that connects the lower jaw to the skull and
allows for movements such as chewing, speaking, and yawning. Magnetic resonance imaging
(MRI) is a noninvasive imaging technique that
uses a strong magnetic eld and radio waves to
produce detailed images of the soft tissues of the
body. MRI has an important role in the diagnosis
and management of TMJ developmental disorders [20, 26].
Temporomandibular Joint: Review of the Anatomy, Pathology, and Magnetic Resonance Imaging…
103
MRI can provide detailed images of the TMJ
and its surrounding structures, including the bones,
muscles, ligaments, and cartilage. This allows for
the identication of abnormalities or changes in the
TMJ that may be indicative of a developmental disorder. For example, MRI can reveal the presence of
a disc displacement, which occurs when the disc
that cushions the TMJ is displaced from its normal
position. This condition is commonly associated
with TMJ pain and dysfunction [28, 36].
MRI can also be used to assess the growth and
development of the TMJ in children. This is particularly important in cases of developmental disorders such as condylar hyperplasia, which is a
condition where there is an overgrowth of the
mandibular condyle, the part of the jaw that articulates with the skull. MRI can provide information
about the size and shape of the condyle, as well as
any changes in the surrounding tissues [32, 33].
In addition, MRI can be used to monitor the
progression of TMJ developmental disorders
over time. This is important in cases where conservative treatments such as physical therapy and
medications are being used. By tracking changes
in the TMJ over time, clinicians can assess the
effectiveness of treatment and make adjustments
as necessary [36].
Overall, MRI plays a valuable role in the diagnosis and management of TMJ developmental disorders. Its ability to provide detailed images of the
TMJ and its surrounding structures allows for the
identication of abnormalities and changes that
may be indicative of a developmental disorder.
MRI can also be used to assess the growth and
development of the TMJ in children and monitor
the progression of TMJ developmental disorders
over time. With its noninvasive nature and high
level of detail, MRI is an important tool in the management of TMJ developmental disorders [12, 34].
4.2 Disc Displacement
Disc displacement is a common condition of the
TMJ that can cause signicant pain and dysfunction. It occurs when the articular disc that separates the condyle and the fossa of the TMJ moves
out of position. The displacement can be anterior,
medial, lateral, or posterior, and it can be associated with derangement of the joint [18, 27, 35].
Magnetic resonance imaging (MRI) is the preferred imaging modality for the diagnosis of disc
displacement, as it provides excellent soft tissue
contrast and can accurately depict the position,
shape, and integrity of the articular disc and other
joint structures. Several studies have demonstrated the high diagnostic accuracy of MRI in
the evaluation of disc displacement, with reported
sensitivity and specicity rates of up to 100% and
96%, respectively [27, 37].
The clinical signicance of disc displacement
is still a matter of debate, as not all displaced
discs are symptomatic, and the association
between disc displacement and joint pain is not
always clear. Some studies have suggested that
disc displacement alone may not be sufcient to
cause pain and that other factors, such as joint
loading and inammation, may play a role in the
development of symptoms [29, 35].
Disc displacement can be categorized into two
subtypes: anterior displacement with reduction
(Fig. 10b) or anterior displacement with no
reduction (Fig.11), depending on whether a normal relationship between the condyle and the
disc is restored during mouth opening [38].
The extent of disc displacement can be classied as complete or partial. Complete displacement occurs when the entire mediolateral
dimension of the disc is displaced, while partial
displacement refers to the displacement of either
the medial or the lateral portion of the disc.
Partial disc displacement, commonly observed in
anterior displacement with reduction, often
involves the anterior displacement of the lateral
part of the disc, while the medial part remains in
its normal position, referred to as rotational disc
displacement. The precise mechanism underlying disc displacement remains unclear; however,
trauma resulting in injury to the posterior disc
attachment is considered the most probable
cause. Unenhanced MRI is the preferred imaging
modality for assessing ID of the TMJ [20, 28].
In the early stages of ID, the disc initially maintains its normal shape, but over time, it undergoes
deformations characterized by thickening of the
posterior band and thinning of the anterior band.
104
ab
F. A. Chagas-Neto et al.
Fig. 11 Anterior displacement with no reduction. (a)
Sagittal proton density-weighted magnetic resonance
imaging (MRI) in the closed-mouth position demonstrates
anterior displacement of the disc (arrow) related to the
articular eminence (a) and anterior to the mandibular con-
This results in the disc assuming a biconvex, teardrop-shaped, or rounded appearance. As long as
the disc remains positioned on top of the condyle
during mouth opening, it maintains a normal
biconcave shape. Consequently, the presence of an
irregular and rounded disc typically indicates disc
dyle (c). (b) Sagittal proton density-weighted MRI in the
open-mouth position demonstrates no reduction of the
disc (arrow) between the articular eminence (a) and the
mandibular condyle (c)
displacement is a rare occurrence. Once again,
these rotational and sideways displacements can
be classied as complete or partial and can occur
with or without disc reduction. Among these patterns, anterolateral displacement is the most commonly observed [24, 39].
disease. Additional MRI ndings suggestive of
disc disease include disc attening, a decrease in
the normal intermediate to high signal intensity of
4.3 Pseudo-Disc
the disc, and the presence of tears or perforations
in the chronic stage [38, 39].
Posterior disc displacement is an uncommon
occurrence (Fig.12), representing only a small percentage of all disc displacements, ranging from 0.01
to 0.001%. The primary clinical manifestation is the
sudden onset of a locked jaw in the open position.
The use of MRI is valuable in diagnosing this condition as it reveals the displacement of the posterior
band beyond the 1 o’clock position on the clock
Pseudo-disc (Fig.13) is a term used to describe
the presence of a band-like structure with low
signal intensity, replacing the typically bright signal of the posterior disc attachment. It is observed
in certain patients who have anteriorly displaced
discs and is believed to be an adaptive reaction to
the displacement, resulting from connective tissue thickening and hyalinization within the pos-
terior disc attachment [37, 40].
face. It is essential to review the patient’s clinical
information before interpreting the images to avoid
mistaking a previous posterior disc plication for an
4.4 Stuck Disc
acquired posterior disc displacement [38, 39].
Rotational displacements encompass anterolateral and anteromedial disc displacements,
whereas sideways displacements include pure
lateral and medial displacements. Isolated lateral
The condition known as the “stuck disc” refers to
a pathological state where the disc remains
immobile in relation to the glenoid fossa and the
articular eminence. This condition can be
ab
Temporomandibular Joint: Review of the Anatomy, Pathology, and Magnetic Resonance Imaging…
105
Fig. 12 Posterior displacement with no reduction. (a)
Sagittal proton density-weighted magnetic resonance
imaging (MRI) in the closed-mouth position demonstrates
posterior displacement of the disc (arrow) related to the
articular eminence (a) and anterior to the mandibular con-
dyle (c). (b) Sagittal proton density-weighted MRI in the
open-mouth position demonstrates no reduction of the
disc (arrow) between the articular eminence (a) and the
mandibular condyle (c)
can lead to pain and joint dysfunction due to limited condylar translation. To accurately diagnose
this condition, it is important to image the temporomandibular joint (TMJ) in both open- and
closed-mouth positions. Sagittal oblique cine
imaging is particularly valuable in assessing the
stuck disc [40, 41].
4.5 Perforated Disc
Disc perforation (Fig. 14) occurs in approximately 5–15% of cases involving displaced joints
and deranged discs. This occurrence is more fre-
Fig. 13 Pseudo-disc. Sagittal proton density-weighted
magnetic resonance imaging (MRI) in the closed-mouth
position demonstrates thickening of the posterior attachments (arrowheads) superior to the mandibular condyle
(c), seen as “pseudo-disc.” Articular disc (arrow) is displaced anteriorly
observed regardless of whether the mouth is open
or closed and is likely caused by adhesions. It
may occur with or without disc displacement and
quent in patients with anterior disc nonreducing
(ADNR) conditions compared to anterior disc
reducing (ADR) conditions, and it is commonly
observed in individuals with advanced arthrosis.
The prevalence of disc perforation is higher in
women than in men, particularly among individuals over 80years of age. MRI ndings associated with disc perforation include disc deformity
(100%), disc displacement (81%), condylar bony
changes (68%), joint effusion (23%), and nonvisualization of the temporal posterior attach-
106
ab
F. A. Chagas-Neto et al.
Fig. 14 Perforated disc. (a) Sagittal proton density-
weighted magnetic resonance imaging (MRI) in the
closed-mouth position demonstrates mild disc perforation
(arrows) in relation to osteophyte of the mandibular con-
dyle (c). (b) Sagittal proton density-weighted MRI in the
closed-mouth position demonstrates extensive disc perforation (arrows) with luxation of the disc fragments. Also,
there is osseous edema in the mandibular condyle (c)
ment (TPA) of the disc (65–68%). Both
conventional and MR arthrograms can aid in
diagnosing disc perforation by demonstrating
opacication of both joint compartments after
injecting a contrast agent into a single lower
compartment. To investigate suspected disc perforation, a fat-suppressed T2-weighted MRI can
be obtained in the sagittal and coronal planes.
Additionally, the absence of stretching or
straightening of the posterior temporal disc
attachment during mouth opening also suggests
the presence of a disc perforation [40–42].
4.6 Joint Eusion andLoose
Bodies
Joint effusion refers to an abnormal accumulation of uid within the joint space and is frequently observed in symptomatic patients
(Fig. 15). In asymptomatic individuals, a small
amount of joint uid can be present. The prevalence of effusion is higher in painful joints compared to non-painful joints. Although not all
patients with joint pain have effusion, those with
large effusions often experience pain and disc
displacement [40, 43, 44].
Fig. 15 Joint effusion. Sagittal proton density-weighted
magnetic resonance imaging (MRI) in the open-mouth
position demonstrates uidlike signal within the articular
space, compatible with joint effusion (arrowheads). Also,
there is anterior displacement of the disc (arrow) in relation to the articular eminence (a) and the mandibular condyle (c)
For evaluating joint effusion, T2-weighted MR
sequences are considered the most effective.
Early-stage effusions typically surround the anterior band, while larger effusions can occupy both
Temporomandibular Joint: Review of the Anatomy, Pathology, and Magnetic Resonance Imaging…
107
the superior and inferior joint spaces. A substantial effusion can provide valuable diagnostic
information, as it delineates the disc and may even
reveal disc perforation and retrodiscal tissue, creating an “arthrography effect.” Gadoliniumenhanced T1-weighted imaging can be useful in
differentiating a plain joint effusion from synovial
proliferation. In patients with inammatory
arthropathies accompanied by synovial proliferation, the proliferating synovium exhibits enhancement, whereas the effusion does not [9, 43, 45].
Loose bodies within a synovial joint can be
classied as primary or secondary synovial chondromatosis (Fig. 16). The primary type occurs
when there is spontaneous cartilaginous metaplasia in the synovium, while the secondary type is
characterized by the incorporation of osseocartilaginous loose bodies within the synovium, often
in the presence of degenerative joint disease.
Typical clinical symptoms associated with loose
bodies include pain, swelling around the ear,
restricted jaw movement, clicking or popping
sounds, and deviation of the jaw to one side during mouth opening. Panoramic radiographs of the
TMJ may or may not reveal the presence of loose
bodies. However, high-resolution CT or MRI
imaging can effectively detect small loose bodies
within the TMJ space [44–46].
4.7 Thickening ofLateral
Pterygoid Muscle Attachment
(Double-Disc Sign)
The specic role of the lateral pterygoid muscle
(LPM) in TMJ function is still a subject of debate,
although it is believed to contribute to generating
side-to-side and protrusive jaw forces.
Electromyographic studies have shown increased
activity in the lower attachment of the LPM in
patients with TMJ internal derangement. Various
morphological changes in the superior and inferior portions of the LPM have been observed on
MRI, including hypertrophy, atrophy, and contractures. These changes have been found to have
a signicant association with clinical symptoms
such as pain or restricted jaw opening in patients
with anterior disc nonreducing TMJ conditions.
It is suggested that there is a notable connection
between anterior disc displacement and attachment of the superior LPM solely to the disc,
rather than to the condyle. Radiologists interpreting imaging should be cautious not to mistake a
thickened inferior LPM for an anteriorly
displaced disc (Fig.17), a phenomenon known as
the “double-disc sign” [16, 17, 20].
Fig. 16 Loose body. Sagittal proton density-weighted
magnetic resonance imaging (MRI) in the open-mouth
position demonstrates a loose body (arrowheads) within
the joint effusion. Also, there is anterior displacement of
the disc (arrow) in relation to the articular eminence (a)
and the mandibular condyle (c)
4.8 Osteochondritis Dissecans
andAvascular Necrosis
Osteochondritis dissecans (OCD) and avascular
necrosis (AVN) of the mandibular condyle share
similar pathological characteristics and likely represent different stages of the same underlying condition. Common clinical features of OCD/AVN
include pain and impaired joint function. Pain is
typically localized to the joint area and along the
distribution of the trigeminal nerve’s third division. Other symptoms may include headache, earache, and muscle spasms in the masticatory
muscles. These symptoms can occur with or without limitations in joint movement [42, 47].
108
Fig. 17 Double-disc sign (thickening of the lateral
pterygoid muscle). Sagittal proton density-weighted
magnetic resonance imaging (MRI) in the closedmouth position demonstrates anterior displacement
of the disc (arrow). The thickened lateral pterygoid
muscle near the mandibular condylar (c) attachment
appears as linear hypointense structure (arrowheads)
inferior to the disc in the same orientation giving the
appearance of “double disc”
a b
F. A. Chagas-Neto et al.
Fig. 18 Avascular necrosis. Sagittal magnetic resonance
imaging (MRI) in the closed-mouth position in proton
density-weighted (a) and on T1-weighted (b) images
demonstrates high marrow signal intensity in proton density image and low signal intensity in T1-weighted image
MRI is the preferred imaging modality for evaluating OCD/AVN of the mandibular condyle. In
cases of AVN, there is a decrease in marrow signal
intensity on T1-weighted sequences. T2-weighted
sequences exhibit variable signal characteristics
depending on the stage of AVN (Fig. 18). Earlystage AVN consistently shows high signal intensity on T2-weighted images, while acute OCD
(Fig.19) typically displays a centrally hypointense
fragment surrounded by a zone of higher signal
within the condylar head. Also, there is an area of low
signal intensity in both sequences, suggestive of subchondral fracture (arrowheads). Articular eminence (a) has
normal signal intensity on both sequences for
comparison
intensity on both T1-weighted and T2-weighted
sequences. Although MRI has a sensitivity of 78%
and specicity of 84% in diagnosing AVN, the
positive predictive value is only 54% due to similar MRI appearances seen in condylar sclerosis
secondary to advanced degenerative changes in
the TMJ. Radiological changes associated with
OCD and AVN of the mandibular condyle often
involve joint effusion and internal derangement of
the disc [42, 47, 48].
Temporomandibular Joint: Review of the Anatomy, Pathology, and Magnetic Resonance Imaging…
lates beyond the boundaries of the anterior
attachment of the TMJ capsule. The condyle
becomes trapped along the anterior slope of the
articular eminence, primarily due to biomechanical constraints related to masticatory muscle
activity [1].
In acute cases, imaging studies are typically
unnecessary since the open lock can be diagnosed based on clinical signs and a relevant history of wide jaw opening or trauma. However, in
chronic cases, MRI can provide valuable information about the height and steepness of the
articular eminences, as well as the shape and
position of the disc [15, 23].
109
Fig. 19 Osteochondritis dissecans. Sagittal proton
density- weighted magnetic resonance imaging (MRI) in
the closed-mouth position demonstrates a tiny bone fragment (arrowhead) at the superior aspect of the mandibular
condyle (c). It can be noted that there is intermediate/high
signal intensity surrounding the bone fragment
4.9 Hypermobility
Patients with a hypermobile temporomandibular
joint (TMJ) may have trouble closing their jaw
(referred to as an “open lock”) following wide
jaw opening. This occurs when the condyle trans-
4.10 Ankylosis
Ankylosis of the TMJ can occur when brous
adhesions or bony fusion restricts the movement
of the jaw (Fig.20). This condition may develop
because of previous infection, trauma, or surgery
or in individuals with juvenile idiopathic arthritis
or bid mandibular condyles. MR arthrography
is a valuable tool for assessing brous adhesions,
while a three-dimensional CT scan is necessary
for surgical planning when bony fusion is suspected [11, 49].
110
ab
F. A. Chagas-Neto et al.
Fig. 20 Ankylosis. Coronal (a) and sagittal reformation (b) of multislice computed tomography (CT) demonstrates
brous ankylosis of the left temporomandibular joint (black arrows)
5 TMJ Tumors andTumorlike
Conditions
The temporomandibular joint (TMJ) is one of the
most complex joints in the human body. It is
responsible for the movement of the lower jaw
and plays an important role in mastication,
speech, and facial expression. TMJ disorders are
a common cause of orofacial pain and dysfunction. Tumors and tumorlike conditions of the
TMJ are relatively rare, but they can cause signicant morbidity and mortality. This section
aims to provide an overview of MRI role in the
most common tumors and tumorlike conditions
of the TMJ [12].
Magnetic resonance imaging (MRI) is a noninvasive imaging modality that is commonly used
in the evaluation of tumors and tumorlike conditions of the temporomandibular joint (TMJ).
MRI provides excellent soft tissue contrast and
multiplanar imaging capabilities, which make it a
valuable tool in the diagnosis and management of
these conditions [32].
5.1 MR Features ofTumorlike
Conditions
MRI is useful in the evaluation of tumorlike conditions of the TMJ, such as synovial chondromatosis, pigmented villonodular synovitis (PVNS),
and osteochondroma. In synovial chondromatosis, MRI typically shows multiple nodular lesions
within the synovial membrane and joint space.
These nodules are hyperintense on T2-weighted
images and hypointense on T1-weighted images.
In PVNS, MRI shows diffuse synovial thickening
with hypointense areas representing hemosiderin
deposition. In osteochondroma, MRI shows a
bony protuberance with a cartilaginous cap that is
hypointense on T1-weighted images and hyperintense on T2-weighted images [46].
5.2 MR Features ofTumors
MRI is also useful in the evaluation of tumors of
the TMJ, such as chondrosarcoma, osteosar-