Osteoarthritis (OA) refers to active and inactive degenerative changes in the cartilage and bone located in the temporomandibular joint (TMJ), which occur due to increased loading of the joint surfaces. In the active form of the disease (osteoarthritis), pain and limited jaw mobility occur, while in the chronic form, crepitus is observed1,2.
It is difficult to determine the exact prevalence of TMJ OA, as radiological features of this condition have been described even in asymptomatic individuals. For this reason, prevalence varies widely from 8% to 60%. When considering age and gender distribution, prevalence is higher in older age groups (25% in the 20-49 age group compared to 70% in the 73-75 age group) and is twice as common in women as in men. Compared to other joints in the body, TMJ OA occurs at a slightly younger age, typically around 35 years old. The etiology is still unknown, but it is assumed to involve multiple risk factors. In addition to age and gender, local factors such as trauma, parafunction, etc., may contribute to the development of the disease. Osteoarthritis can be classified in terms of etiology as primary (idiopathic) or secondary, where the cause of the arthritic changes is known (e.g., trauma, infection)3.
Clinical diagnostics include medical history and a clinical examination. The medical history provides subjective symptoms about the presence, intensity, duration, and spread of pain, as well as the presence of other systemic diseases. The clinical examination reveals objective signs of the disease1,2. The standardization of the diagnostic protocol is guided by the guidelines of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD)4.
A definitive clinical assessment and confirmation or reevaluation of the clinical diagnosis are confirmed by radiological diagnostics. The two main radiological presentations of the disease are degenerative, with erosions and subchondral cysts, and proliferative, with osteophytes and sclerosis, which may change over time due to remodeling5. According to the recommendations of the American Academy of Oral and Maxillofacial Radiology, changes in bone structures should be assessed using CT or CBCT6. CBCT reduces artifacts and radiation dosage, while still providing equally high-quality images of bone. CBCT allows for the visualization of the morphology and integrity of the joint surfaces and subcortical bone, as well as the assessment of condylar volume7. The contribution of MRI to diagnosing OA lies in visualizing soft tissue structures, and it is the only radiological method that provides an excellent view of the appearance and position of the intraarticular disc and abnormalities in the bone marrow of the condyle, and it is also good for detecting joint effusion6.
Along with clinical criteria, radiological criteria have been developed for standardized reporting and selecting the optimal imaging method for various TMJ diseases. In the case of TMJ OA, CT is the reference standard for diagnosis, and to confirm this diagnosis, at least one of the following criteria must be met: subchondral cysts, erosions, generalized sclerosis, osteophytes, or free calcified bone bodies. Flattening and/or cortical sclerosis are considered indeterminate findings that could represent a normal variant, aging, remodeling, or be precursors to degenerative changes8. Degenerative changes more commonly affect the joint surfaces of the mandibular condyle than the temporal bone. When recognizing radiological characteristics, it is important to note that erosions are characteristic of the early stage, while osteophytes, sclerosis, and flattening are indicative of advanced disease7. In patients with long-term or permanent disc displacement, especially with anterior displacement without reduction, leading to subsequent hypomobility of the condyle, OA development is expected9.
Structural changes are often not in line with symptoms, which raises questions about their clinical significance. According to existing literature, the most reliable associations are between TMJ pain and joint effusion, bone marrow edema in the condyle, advanced deformities of the condyle with erosions, and anterior disc displacement without reduction10.
This study included 124 patients (248 TMJs) who, according to DC/TMD, meet the criteria for TMJ OA after medical history and clinical examination and in whom CBCT and MRI of both TMJs were performed after the clinical suspicion of TMJ OA was raised. The study excluded patients for whom OA was the result of a systemic disease (e.g., rheumatoid arthritis) or trauma and patients with previous interventions in the TMJ area. Before the start of the study, participants were provided with an Informed Consent Form.
After the clinical examination, anamnesis data were collected regarding pain (which side of the jaw, duration, and intensity of pain according to the VAS scale). A manual functional analysis was performed to determine the tenderness of the bilaminar zone. Radiological images of the TMJs (a total of 248 joints imaged on CBCT and MRI) were analyzed by a radiology resident and a head and neck radiologist. Thin-slice 3D reconstructions were made from the CBCT scans with the mouth closed in axial, coronal, and sagittal planes. MRI sequences used for analysis included oblique sagittal T1 and T2 weighted images with closed mouth and proton-density (PD) images with both closed and open mouth.
The radiological interpretation of the CBCT and MRI findings was based on the RDC/TMD guidelines. For each TMJ, the presence of key bony changes critical for the diagnosis of TMJ OA was assessed: subchondral cysts,
