Structure and Development of the Temporomandibular Joint
- Joint capsule
- Articular disc
- Mandibular condyles
- Articular surface of the temporal bone
- Temporomandibular ligament
- Capsule is a thin, loose envelope attached to mandibular fossa and articular tubercle
- Articular disc is composed of dense fibrocartilagenous tissue and divides the joint into upper and lower compartments
- Ligaments include the temporomandibular ligament, stylomandibular ligament, and sphenomandibular ligament
- Joint formation begins around 12 weeks of gestation
- Mesenchyme forms the fibrous joint capsule
- The developing lateral pterygoid muscle attaches to the fetal disc
- The disc extends posteriorly through the petrotympanic fissure and attaches to the middle ear
- The mandibular condyle has a growth center with hyaline cartilage that allows for bone growth

Function and Jaw Movement of the Temporomandibular Joint
- Temporomandibular joint is a ginglymoarthrodial joint, combining hinging and sliding movements
- Mandibular condyle articulates with the temporal bone in the mandibular fossa
- An articular disc divides the joint into two compartments
- Rotation occurs in the lower compartment, while translation occurs in the upper compartment
- Resting position of the joint allows for a 2-4mm interocclusal clearance
- Normal full jaw opening is 40-50 millimeters
- Mandible moves during jaw movements, not the maxilla
- Excursions include lateral movements, forward (protrusion), and backward (retrusion) movements
- Protrusion involves translation of the condyle without significant rotation

Clinical Significance and Pathologic Conditions of the Temporomandibular Joint
- Temporomandibular joint pain can be caused by myofascial pain dysfunction syndrome
- Internal derangements, such as disc displacement, can also cause pain
- Osteoarthritis is a degenerative joint disease affecting the temporomandibular joint
- Temporal arteritis can cause pain and is considered a diagnostic criteria
- Temporomandibular joint dysfunction (TMD) refers to a group of problems affecting the joint and associated tissues
- Chondrosarcoma and osteosarcoma are rare conditions that can affect temporomandibular joint function
- Other conditions may cause pain and swelling in the joint
- Proper diagnosis and treatment are essential for managing these pathologic conditions
- Regular dental and medical check-ups can help detect and address any issues with the temporomandibular joint

Examination and Disc Displacement in the Temporomandibular Joint
- Temporomandibular joints can be felt in front of or within the external acoustic meatus during mandibular movements
- Auscultation of the joint can be performed
- The most common disorder of a temporomandibular joint is disc displacement
- Disc displacement occurs when the articular disc moves out from between the condyle and the fossa
- Disc displacement is usually very painful
- The articular disc is attached anteriorly to the superior head of the lateral pterygoid muscle and posteriorly to the retrodiscal tissue
- Disc displacement causes the mandible and temporal bone to make contact on something other than the articular disc
- In most instances of disc displacement, the disc is displaced anteriorly upon translation
- Disc displacement with reduction is characterised by a pop or click sound upon opening and closing of the mouth

Temporomandibular Disorder (TMD) and Fibromyalgia
- TMD is pain and dysfunction of the TMJ and the muscles of mastication
- TMD represents a range of distinct disorders with multifactorial etiology
- TMD is the second most frequent cause of orofacial pain after dental pain
- The pathophysiology of TMD is poorly understood
- TMD accounts for the majority of pathology of the TMJ
- Fibromyalgia is a condition associated with TMD
- Fibromyalgia is characterised by widespread musculoskeletal pain and fatigue
- Fibromyalgia is more common in women than in men
- The exact cause of fibromyalgia is unknown
- Fibromyalgia often coexists with other chronic pain conditions