What are the different types of disc displacement in the temporomandibular joint (TMJ) and their management options?

Types of Disc Displacement in the Temporomandibular Joint

Disc displacement in the TMJ is classified into four main types based on direction and reducibility: anterior disc displacement with reduction (DDWR), anterior disc displacement without reduction (ADDwoR), posterior disc displacement (rare), and lateral/medial disc displacement, with the vast majority being anterior displacements that represent only 5% of all TMD cases since 85-90% of TMD is muscular in origin. 1

Anterior Disc Displacement With Reduction (DDWR)

Clinical Characteristics

• The disc is displaced anteriorly when the mouth is closed but reduces (returns to normal position) during mouth opening, producing a characteristic clicking or popping sound 2
• This is the most common type of intra-articular TMJ disorder 2
• DDWR is usually asymptomatic and requires no treatment, as TMJ structures adapt very well and painlessly to different disc positions 2
• Clicking may occur during opening, closing, or both (reciprocal clicking) 3, 2

Natural Course and Prognosis

• DDWR is mostly a stable, pain-free, lifelong condition representing just a "noisy annoyance" for most patients 4
• Long-term studies demonstrate favorable progression with no pain or jaw locking occurring in most patients 2
• Only a small minority of DDWR patients progress to disc displacement without reduction 4

Management Approach

• No active treatment is warranted for asymptomatic DDWR, even when clicking is present 2, 4
• Patient education and reassurance about the benign nature of the condition 2
• Treatment is only indicated if pain develops or mechanical symptoms worsen 1, 4

Anterior Disc Displacement Without Reduction (ADDwoR)

Clinical Characteristics

• The disc is displaced anteriorly and does not reduce during mouth opening, resulting in limited mouth opening (closed lock) and often joint pain 5, 4
• Most patients experience limited mouth opening and joint pain simultaneously 5
• The displaced disc acts as a mechanical obstruction preventing full condylar translation 5

Temporal Classification

• Acute ADDwoR (within 2 months): Manual therapy may successfully reposition the disc, followed by splint therapy and movement exercises to maintain disc-condyle relationship 5
• Chronic ADDwoR (beyond 2 months): Disc repositioning becomes less likely; focus shifts to functional restoration rather than anatomical correction 5

Management Strategy

• The treatment goal is symptom resolution and functional restoration through "3M techniques" (modality, manual, and movement therapy) rather than disc repositioning 5
• Physical therapy focuses on joint function instead of the displaced disc position 5
• Surprisingly, only in rare cases does loss of disc reduction result in persistent closed lock symptoms, as signs and symptoms tend to reduce and often resolve within months 4
• Conservative non-surgical treatment is the primary option, focusing on speeding up natural pain alleviation and mouth opening improvement 4
• Enhanced health education and multidisciplinary cooperation are essential for successful management 5

Posterior Disc Displacement

Clinical Characteristics

• Posterior disc displacement is a rare TMJ disorder with the main clinical sign being sudden molar open-bite (jaw locked in the open position) 6
• Patients may experience a sensation of intra-articular foreign body and rarely joint pain 6
• Joint sounds are typically unremarkable, distinguishing it from anterior displacements 6
• Mouth opening may be slightly impaired 6

Classification

• Like anterior displacements, posterior disc displacements can theoretically be classified as reducible or nonreducible 6

Diagnosis and Management

• Definitive diagnosis requires MRI evaluation 6
• Conservative treatment should always be attempted before irreversible invasive therapy, as it can be successful in patients with functional impairment 6
• No consensus exists concerning optimal treatment 6

Lateral and Medial Disc Displacement

Clinical Context

• These represent less common directional variants of disc displacement 7
• Often occur in combination with anterior displacement (anteromedial or anterolateral) 8
• The most common pattern is anterior-medial displacement of the articular disk 8

Diagnostic Imaging Considerations

Imaging Modality Selection

• MRI is considered the gold standard for ligament and articular capsule structure analysis, including disc position evaluation 7
• CT/CBCT is the gold standard for bone lesion assessment but not for disc evaluation 7
• Radiological examination is only indicated when insufficient information is obtained from anamnestic-clinical examinations 7

Pediatric Considerations

• Internal derangement (disc displacement with or without reduction) is among the most frequently found TMJ disorders in pediatric age 7
• The prevalence of TMD signs and symptoms increases with age, supported by important scientific evidence 7

Critical Clinical Pitfalls

Overtreatment of Asymptomatic Conditions

• The most important pitfall is assuming that all clicking or popping represents pathology requiring intervention 3
• Crepitus alone without pain or other mechanical symptoms may represent normal joint sounds that do not require surgical intervention 3

Misidentification of Non-Mechanical Symptoms

• Pain alone without locking, catching, or clicking does not indicate intra-articular structural pathology requiring advanced imaging or surgical intervention 3
• Stiffness that improves with warm-up rather than mechanical blocking suggests muscular rather than disc pathology 3

Premature Surgical Intervention

• The favorable natural course of disc displacements only warrants active treatment for symptomatic disc displacements without reduction 4
• Invasive procedures should not be pursued before exhausting conservative options 9
• Only when end-stage intra-articular disease develops do patients require invasive interventions such as arthroscopy or joint replacement 1

Misdiagnosis of TMJ vs. Muscular Pathology

• Approximately 50% of patients presenting with TMJ-region symptoms have complications unrelated to the TMJ itself, emphasizing the importance of accurate differential diagnosis 1
• The vast majority (85-90%) of TMD patients can be treated effectively with non-invasive interventions, as the underlying cause is typically muscular rather than structural 1