Physiology of the Visual Analogue Scale and Articular Disc

Temporomandibular Joint Disorders: Diagnosis and Classification

• Temporomandibular joint (TMJ) disorders (TMD) are conditions affecting the TMJ, causing pain and restricted jaw movement.
• The TMJ is an atypical synovial joint, permitting both hinge and gliding motions.
• It shares some features with other synovial joints (disc, fibrous capsule, fluid, synovial membrane, ligaments).
• However, the TMJ's articular surface is covered by fibrocartilage, not hyaline cartilage.

Outline

• The TMJ complex
• Biomechanics of the TMJ
• Etiology
• Clinical features
• Examination
• Diagnosis and Classification

The TMJ Complex

• The TMJ complex consists of the joint, ligaments, and muscles.
• The joint includes the condyle, glenoid fossa, articular disc, and joint capsule.

Biomechanics of the TMJ

• The articular disc is tightly bound to the condyle by lateral and medial discal ligaments.
• Rotation of the disc on the articular surface of the condyle is the only physiological movement between these surfaces.
• The condyle-disc complex allows for rotational movements within the TMJ.
• A second system involves the condyle and disc complex acting against the mandibular fossa.
• Free sliding movement is possible between these surfaces in the superior cavity, occurring when the mandible is moved forward, referred to as translation.
• Translation takes place between the superior surface of the articular disc and the mandibular fossa within the superior joint cavity.

Etiology

• TMDs are multifactorial, involving biological and psychological factors.
• Depression, lack of sleep, and stress-related disorders can influence TMD development.
• Patients with TMD often have lower pain thresholds.
• Relationship between TMD and parafunctional habits (bruxism and clenching) is inconsistent.
• Occlusal interferences, malocclusions, and orthodontics are of minor importance in TMD etiology.
• Trauma (macro-trauma to head/neck, micro-trauma like dental treatment) may contribute to TMD in predisposed patients, impacting intracapsular disorders more than muscular ones.
• Increased emotional stress increases head and neck muscle tonicity and non-functional muscle activity (bruxism/clenching).

Clinical Features

• Presenting symptoms often involve pain in one or more masticatory muscles (localized or generalized).
• Pain in TMJ during palpation or movement.
• Clicking, popping, or crepitus with or without locking.
• Decreased mouth opening.
• Headache in the temporal region.
• Otalgia (ear pain) in the absence of aural disease.

Examination

• A detailed clinical interview and thorough physical inspection are essential for examination.
• Imaging and additional tests are rarely needed (approximately 70% of diagnosis is based on history).
• Mandibular AROM (active range of motion), standardized TMJ/masticatory/cervical muscle palpation, and inspection of articular sounds are needed.
• Asking about the onset of the problem, previous diagnoses, and treatments is important.
• Chief complaints, medical history, dental history, systems review, and psychosocial history must be collected.

TMJ Evaluation

• Assessing TMJ range of motion (ROM) involves measuring inter-incisal distance and overbite.
• Evaluating the mandibular opening and closing movements is assessed by their path, looking for deviations.
• Normal range is 10-14 mm in protrusion, 10 mm toward right/left.
• Minimum opening is around 30 mm (3 fingers width).
• Max. opening without discomfort is around 40-60 mm.

Detection of Joint Sounds

• Presence of joint sounds during mouth opening and mandibular excursion can aid in diagnosing disc-condyle coordination issues.
• Using a stethoscope is reliable for detecting articular sounds.
• Clicking and crepitation are common sounds in TMD patients.

TMJ Palpation

• Tenderness to palpation is a significant indicator of intracapsular pathology.
• The joint should be palpated bilaterally, and any pain should be noted.
• Muscles of the temporalis (3 portions), masseter (superficial/deep), the insertion of the medial pterygoid are also examined.
• Lateral pterygoid is assessed with resisted movement tests.

Occlusion

• Occlusion is assessed for tooth wear or fractured restorations, and soft tissue is reviewed for tongue scalloping, frictional keratosis, and linea alba on the buccal mucosa.

Imaging

• Radiographs (DPT) are mostly adjunctive and used for bony pathology/fracture assessment.
• MRI is the optimal modality for comprehensive joint assessment, focusing on soft tissues (disc).

Diagnosis and Classification

• Muscle disorders (local myalgia, myofascial pain, myofascial pain with referral).
• Disc displacement (with reduction, without reduction).
• Other disorders (arthralgia, osteoarthritis, osteoarthrosis).

Acute vs Chronic TMD

• Acute TMD often has a clear cause (stress, trauma), short-duration, and resolves with rest, diet, and analgesia.
• Chronic TMD lasts longer than 3 months, can be biopsychosocially destructive, and may lead to depression/chronic pain behaviors.

This quiz covers the primary functions and characteristics of the Visual Analogue Scale (VAS) and the articular disc in joints. It explores common applications, limitations, and the anatomical details related to the articular disc. Test your knowledge on these important physiological concepts.