The temporomandibular joint (TMJ) is a diarthrodial joint,
formed by the squamous portion of the temporal bone and the condyle of the
mandible. These two osseous elements are enclosed into a fibrous capsule and
articulate with each other by an interposed disc of connective tissue.
The disc is
fixed to the articular capsule and the lateral margins of the condyle. The
joint cavity is therefore divided into an upper and a lower compartment. A
synovial membrane lines the inner side of the capsule and disc, except for the
articulating surfaces. Synovial fluid produced by this lining membrane fills
the joint compartments.
The TMJ is responsible for all movements of the jaw, which take
place in different orthogonal planes and around multiple axes of rotation. In
these movements, the articular disc plays a major role in compensating the
incongruities of the articular surfaces. In the mandibular opening-closing
movement, for instance, the condylar head rotates and translates relative to
the temporal bone with a simultaneous gliding of the disc. Several theories
have been proposed to explain the mechanism that coordinates the disc-condyle
complex during jaw movements.The biomechanical properties of the disc are
largely involved in this coordination.
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| Normal Radiographic anatomy of TMJ |
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| Normal Radiographic anatomy of TMJ |
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| Normal Radiographic anatomy of TMJ |
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| Normal Radiographic anatomy of TMJ |
Internal
Derangements
- General orthopedic term
implying a mechanical fault that interferes with the smooth action of a
joint
- The most common internal
derangement is disc displacement
Clinical
Features
- Clicking sounds from joint(s)
- Restricted or normal mouth opening
capacity
- Deviation on opening
- Pain
Imaging Features
- Anterior
disc displacement: posterior band of the disc located anterior to the
superior portion of the condyle at closed mouth on oblique sagittal images
- Disc may have normal (biconcave) or
deformed morphology
- In opened mouth position disc may be in a
normal position (“with reduction”) or continue to be displaced (“without
reduction”)
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| Partial anterior disk displacement at baseline |
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Complete anterior
disc displacement
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| Lateral disk displacement and normal bone |
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| Medial disk displacement |
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| Posterior disk displacement |
Osteoarthritis
Definition
- Non-inflammatory focal
degenerative disorder of synovial joints, primarily affecting articular cartilage
and sub-condylar bone; initiated by deterioration of articular soft-tissue
cover and exposure of bone.
Clinical
Features
- Crepitation sounds from
joint(s)
- Restricted or normal mouth
opening capacity
- Pain or no pain from joint areas and/or
of mastication muscles
- Occasionally, joints may show
inflammatory signs
- Women more frequent than men
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anteriorly displaced and
deformed, degenerated disc and irregular
cortical outline with osteophytosis and sclerosis of condyle .
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Advanced osteoarthritis and anterior disc displacement,
with joint effusion
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Bone Marrow Abnormalities
Definition
- Bone marrow edema: serum
proteins within marrow interstitium surrounded by normal hematopoietic
marrow.
- Osteonecrosis: complete loss of
hematopoietic marrow.
Imaging
Features
• Abnormal signal on T2-weighted image
from condyle marrow: increased signal indicates marrow edema; reduced signal
indicates marrow sclerosis or fibrosis
• Combination of marrow edema signal
and marrow sclerosis signal in condyle most reliable sign for histologic
diagnosis of osteonecrosis
• Marrow sclerosis signal may indicate
advanced osteoarthritis without osteonecrosis, or osteonecrosi
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| Bone marrow abnormalities |
Arthritides
Definition
- Inflammation of synovial
membrane characterized by edema, cellular accumulation, and synovial
proliferation (villous formation).
Clinical
Features
- Swelling of joint area, not
frequently seen in TMJ
- Pain (in active disease) from joints
- Restricted mouth opening
capacity
- Morning stiffness, in particular stiff
neck
- Dental occlusion problems; “my bite
doesn’t fit”
- Crepitation due to secondary
osteoarthritis
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| Rheumatoid arthritis |
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| Rheumatoid arthritis |
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| Psoriatic arthropathy |
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| Psoriatic arthropathy |
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| Inflammatory arthritis |
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| Ankyloses |
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| Growth disturbances of TMJ |
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| Condylar hyperplasia and facial asymmetry |
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| Bifid condyle |
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| inflammatory and tumor like conditions |
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| Benign tumors like TMJ |
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| Synovial chondromatosis |
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| Osteochondroma |
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| osteoma |
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| Malignant tumors |
