Temporomandibular joint (TMJ) disorders are multifactorial. Internal derangement (ID)—an abnormal positional relationship between the disc, condyle, and articular eminence—has been reported in up to 70% of symptomatic patients and is commonly staged using the Wilkes system (Stages I–V), which links progressive disc displacement to escalating pain and structural damage. Degenerative joint disease (DJD) is typically noninflammatory and characterized by cartilage deterioration, subchondral remodeling, osteophyte formation, and secondary synovitis. Mechanical overload from trauma, parafunction, occlusal instability, and repetitive loading may exceed the adaptive capacity of the disc and retrodiscal tissues. Structural abnormalities are present in approximately 25% of asymptomatic individuals, which establishes a critical surgical principle: imaging findings must be correlated with clinical examination before they drive operative decisions.

The TMJ is a ginglymoarthrodial articulation formed by the mandibular condyle and the temporal bone—specifically the glenoid fossa and articular eminence ( Fig. 1 ). The temporal component comprises the glenoid fossa posteriorly and the articular eminence anteriorly ( Figs. 2 and 3 ). The glenoid fossa is bounded posteriorly by the tympanic plate and anteriorly by the articular tubercle. Mean glenoid fossa depth is 7.5 mm and mean articular eminence inclination is 49.9°. The roof of the glenoid fossa is notably thin (mean ∼0.9 mm) —a surgically relevant threshold given that this bone separates the joint from the middle cranial fossa during arthroscopic puncture and elevator instrumentation. Steeper eminence inclinations increase translational demands on the disc-condyle complex and are associated with greater disc displacement severity; flatter eminences predispose to posterior condylar positioning and altered loading. ^,

Anatomic landmarks of the skull.

TMJ osseous anatomy sagittal view.

TMJ osseous anatomy axial view.

Normal condylar morphology is characterized by a smooth cortical outline with trabecular bone oriented along principal stress trajectories ( Figs. 4 and 5 ). Cortical thinning, surface flattening, and trabecular disorganization may represent adaptive remodeling rather than frank pathology ; osteophyte formation, subchondral sclerosis, and contour change likewise occur in asymptomatic individuals. The surgical implications are twofold: preoperative CT or CBCT should define the relationship of the fossa roof to planned arthroscopic trajectories, and condylar morphology must inform prosthesis fit and screw-purchase planning in alloplastic reconstruction.

CT of normal condylar morphology coronal view.

CT of normal condylar morphology sagittal view.

The articular disc is a biconcave fibrocartilaginous structure interposed between the condyle and the temporal component ( Fig. 6 ). The disc is composed of dense collagen with regional thickness variation—approximately 3 mm posteriorly, 1 mm in the intermediate zone, and 2 mm anteriorly ^, —and is relatively avascular and aneural. The bilaminar (retrodiscal) zone is highly vascularized and innervated, containing elastic fibers that permit anterior disc translation during mandibular movement. ^,

Normal TMJ soft Tissue and disc anatomy.

MRI is the standard for evaluation of disc position, morphology, and associated soft-tissue pathology ( Figs. 7–9 ). Disc displacement is classically categorized as anterior displacement with or without reduction, based on the disc-condyle relationship in closed- and open-mouth positions. Displacement severity correlates with joint effusion, retrodiscal inflammation, and disease progression, although displacement alone does not reliably predict symptom severity ( Fig. 10 ). Inflammatory change within the retrodiscal tissues—rather than disc position itself—appears to be the primary pain generator in many patients ( Fig. 11 ). These distinctions are operatively decisive: isolated displacement without effusion or retrodiscal signal change favors arthroscopic lysis and lavage; effusion plus retrodiscal inflammation supports arthroscopy with disc repositioning; a deformed, perforated disc with advanced DJD favors discectomy or alloplastic reconstruction.

T1 weighted MRI showing normal disc position, sagittal view closed mouth.

T1 weighted MRI showing normal disc position, sagittal view open mouth.

T1 weighted MRI showing normal disc position, coronal view closed mouth.

T2 weighted MRI showing joint effusion, sagittal view.

Arthroscopy showing inflamed retrodiscal Tissue.

The TMJ capsule encloses the joint and contributes to stability, proprioception, and synovial fluid containment, with sensory innervation that mediates joint position sense and pain. Capsular distention—visualized on MRI as joint effusion or synovitis—correlates with arthralgia and functional limitation. Collateral ligaments anchor the medial and lateral disc margins to the condyle, ensuring coordinated disc-condyle motion; the temporomandibular, sphenomandibular, and stylomandibular ligaments provide secondary restraint ( Fig. 12 ). Ligamentous structures themselves are inconsistently visualized on MRI.

Collateral and secondary ligaments of the TMJ.

The medial aspect of the TMJ is a zone of heightened surgical risk: major neurovascular structures may lie within millimeters of the medial capsule. The rule of 2s provides a practical framework—the lateral capsule lies approximately 2 cm from the skin, the medial capsule approximately 2 cm medial to the lateral capsule, and major vascular and neural structures approximately 2 cm medial to the medial capsule.

Vascular anatomy is highly variable. The maxillary artery may course medial or lateral to the lateral pterygoid muscle ( Fig. 13 ); its branches—masseteric, deep temporal, and middle meningeal—contribute to the periarticular blood supply ( Fig. 14 ). Quantitative cadaveric and angiographic data establish the working distances: the middle meningeal artery averages 19 mm from the condylar apex and 15 mm from the medial condylar point, the maxillary artery lies within 6 to 7 mm of the sigmoid notch, and the masseteric artery may be as little as 4 mm from the condylar neck, 3 mm from the articular tubercle, and 1 mm from the sigmoid notch. Venous drainage occurs primarily through the pterygoid venous plexus ( Fig. 15 ), a low-pressure, high-volume bleeding source difficult to control once entered. Superficial temporal vessels are at risk during preauricular incision. CT angiography is useful in revision and complex cases for defining vascular relationships before incision.

Internal maxillary artery relationship to the condylar neck.

Arterial supply of the TMJ.

Venous drainage of the TMJ.

Sensory innervation of the TMJ is primarily from the auriculotemporal nerve, a branch of V3. The nerve courses posterior and medial to the condylar neck and frequently contacts the capsule and posterior discal tissues, providing an anatomic basis for referred otologic and temporal pain. Entrapment by inflamed retrodiscal tissues has been proposed as a mechanism in TMJ pain syndromes.

The temporal branch of the facial nerve is the principal motor structure at risk during open TMJ approaches. Cadaveric studies place this branch within 3 to 10 mm of the lateral condylar pole and crossing the zygomatic arch between 8 to 35 mm anterior to the bony external acoustic meatus ( Fig. 16 ). Imaging cannot reliably visualize the nerve; protection is achieved surgically by dissecting deep to the superficial layer of the deep temporal fascia above the arch, minimizing anterior retraction, and avoiding electrocautery within the danger zone ( Figs. 17 and 18 ).

Anatomy of the temporal branch of the facial nerve.

Surgical dissection of the TMJ capsule.

Preauricular and endaural incision designs.

Clinical examination alone has poor agreement with imaging-confirmed ID or osteoarthritis, so imaging is typically required to establish the presence, severity, and extent of intra-articular disease ( Table 1 ).

Table 1

Imaging modality strengths and limitations

Modality	Best for	Strengths	Limitations
Panorex	Initial screening	Fast, cheap, widely available; gross condylar morphology, asymmetry, fractures, advanced osteoarthritis (OA)	Poor TMJ detail; 2D distortion; cannot assess disc, effusion, and synovitis
MRI	Soft tissue/TMJ internal derangement (IPD)	Gold standard for disc position/morphology, effusion, synovitis, retrodiscal inflammation, and marrow edema	Limited bony detail; costly; motion artifact; longer study time
CT	Osseous disease/advanced OA	Best for erosions, osteophytes, sclerosis, ankylosis, fractures; excellent for surgical planning/TJR workup	Radiation; limited soft tissue evaluation
CBCT	Outpatient bony evaluation	High bony resolution with lower radiation than CT; excellent condyle/fossa remodeling, OA changes	Cannot evaluate disc or inflammation; less ideal for complex reconstruction planning than CT

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