Anatomical basis and core of the problem
To understand the pathogenesis of arthrosis, one must be familiar with key joint structures. Normally, harmonious movement is ensured by:
- Articular tubercle of the temporal bone (tuberculum articulare ossis temporalis);
- Articular disc (discus articularis);
- Mandibular condylar process (processus condylaris mandibulae, also known as the mandibular head).
TMJ disorders most frequently begin with a disruption of spatial relationships between these structures. Due to constant microtrauma and strain on the intra-articular ligaments, reactive synovitis may develop — an inflammatory process accompanying virtually any clinical form of internal derangement.
From subluxation to arthrosis: stages of joint degradation
Secondary osteoarthritis does not appear suddenly. It is preceded by a cascade of pathological changes associated with articular disc displacement:
- Articular disc subluxation. This is the initial stage. The disc is displaced anteriorly, but reduces back under the articular tubercle upon mouth opening. The patient notices clicking sounds, while the range of motion remains fully preserved.
- Recurrent articular disc dislocation. The degree of displacement increases. Periodically, the ligaments fail to perform their function, and the disc blocks the movement of the condylar process. Episodes of restricted jaw mobility occur (ranging from minutes to hours), which resolve either spontaneously or following manual patient manipulation.
- Chronic articular disc dislocation. The ligaments of the bilaminar zone are irreversibly damaged. The disc permanently assumes an anteromedial position and no longer reduces. The patient complains of pain, a history of joint noises, and severe restriction of mouth opening (less than 2.5 cm between the incisors). When attempting to open the mouth, the jaw deviates toward the affected side.
Secondary osteoarthritis: the finale of internal derangements
If a chronic irreducible dislocation persists for more than six months, the process progresses to the stage of secondary osteoarthritis. This is a severe morphological lesion of the joint.
Pathomorphology of TMJ arthrosis:
- The shape of the articular disc is grossly distorted (compression, kinking, or even tearing occurs).
- Intra-articular adhesions (adhesions) develop.
- The deformed disc becomes tightly fused with the outer surface of the mandibular head and the posterior slope of the articular tubercle.
- Cartilage coverage is destroyed, and defects appear.
- Bony structures are deformed, with osteophytes proliferating along the margins.
Clinically, this manifests as excruciating pain that is constant and sharply intensifies with the slightest attempt at movement. Excursion of the mandibular head is virtually blocked. Radiographs and MRIs clearly visualize progressive changes in the contours of the condylar process and articular tubercle.
Rare form: chronic posterior dislocation
In contrast to typical anterior displacement, rare cases involve chronic posterior articular disc dislocation. With the mouth closed, the disc lies posterior to the condylar process, and during movement, it becomes trapped between the mandibular head and the posterior wall of the mandibular fossa.
Specific clinical features of posterior dislocation:
- The patient cannot tightly close the teeth (pain sharply increases when attempting maximum contact).
- The mandible on the affected side is protruded forward.
- The chin is shifted (deviated) toward the healthy side.
- Laterotrusion (lateral movement) toward the affected side is restricted and painful.
- Meanwhile, the amplitude of simple mouth opening is practically unaffected.
Briefly: answers to topical questions
What anatomical structures form the temporomandibular joint?
The temporomandibular joint is formed by the following main anatomical structures:
- Mandibular head (caput mandibulae) — the ellipsoid extremity of the mandibular condylar process (processus condylaris mandibulae).
- Mandibular fossa of the temporal bone (fossa mandibularis) — an oval depression between the base of the zygomatic process and the external acoustic meatus.
- Articular tubercle of the temporal bone (tuberculum articulare ossis temporalis) — a cylindrical eminence located anterior to the mandibular fossa.
- Articular disc (discus articularis) — a structure that divides the joint cavity into two isolated compartments (superior and inferior).
What radiographic signs are characteristic of TMJ arthrosis?
Osteoarthritis of the temporomandibular joint is characterized by the following radiographic features:
- Narrowing of the joint space — accompanied by impaired function of the mandibular head.
- Subchondral sclerosis — compaction of the terminal plates of the bony joint elements.
- Osteophytosis — formation of bony projections (spurs), most frequently in the region of the mandibular head.
- Deformation of bony structures — flattening and irregularity of the contours of the articular surfaces, with the mandibular head acquiring a club-like shape.
- Cystic restructuring — focal subchondral radiolucencies (Ely cysts / Ely cyst).
Which ligaments reinforce the temporomandibular joint?
The ligamentous apparatus of the temporomandibular joint is formed by fibrous inelastic connective tissue and is divided into three groups:
- Intracapsular ligaments — include two pairs. The first fixes the articular disc to the temporal bone; the second runs from the lateral margins of the disc to the lateral surfaces of the condylar neck.
- Extracapsular ligaments — these include the lateral (temporomandibular) ligament, which lies outside the joint capsule and is the only proper joint ligament.
- Accessory ligaments — pertain to the joint but are not connected to the joint capsule.
What treatment methods are used for secondary TMJ osteoarthritis?
Osteoarthritis of the temporomandibular joint (including secondary osteoarthritis developing against the background of chronic disc dislocation) is managed with complex treatment:
- Orthopedic treatment — rational prosthetics to eliminate abnormal occlusal contact.
- Drug therapy — prescription of nonsteroidal and steroidal anti-inflammatory drugs, as well as chondroprotective agents.
- Physiotherapy — magnetotherapy, ultraphonohoresis with hydrocortisone to relieve concomitant inflammation.
- Surgical treatment — indicated for severely impaired mandibular function; includes reshaping of the mandibular head (removal of deforming parts) and articular disc plication.
If necessary, a rheumatologist consultation is also scheduled.
How to remember chin deviation: in chronic disc dislocation (and arthrosis), the jaw shifts TOWARD THE AFFECTED joint, whereas in rare posterior disc dislocation, it shifts toward the HEALTHY side.
Class and exam questions
Habitual dislocation always occurs after a previous acute dislocation, and targeted reduction (by the patient or a doctor) is always required to return the jaw to its place. In chronic dislocation, the condyle reduces itself during movements.
Habitual dislocation always has a history of an acute dislocation episode, and targeted manual reduction is strictly required to return the joint to normal. In chronic dislocation, the jaw reduces spontaneously during articulation.
How to differentiate articular disc subluxation from mandibular condyle dislocation?
Key feature: in disc subluxation, the condylar process does not leave the mandibular fossa even at maximum mouth opening. In dislocation, the condylar head moves excessively anteriorly, past the apex of the articular tubercle.
What imaging modality is considered the best for TMJ pathology?
The recommended method is magnetic resonance imaging (MRI). Only MRI allows reliable dynamic assessment of the soft-tissue articular disc position (during mouth opening and closing).
What else to study on this topic
- Biomechanics of chronic mandibular condyle dislocation
- Specifics of "early" and "late" joint clicks
- Types of articular disc deformation (bending, compression, tearing)
- Pathogenesis of locking in recurrent disc dislocation
Master the entire topic in the course "Surgical Dentistry"
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "TMJ Arthrosis" and 866 more pages on the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 28 video lessons on the subject
Other topics in "Chapter 13. Temporomandibular Joint Disorders (V.V. Bekreev)"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.