Clinical Significance of Changes in the Bone Marrow and Intra-Articular Soft Tissues of the Temporomandibular Joint

Patients with facial pain and jaw function problems constitute a large and heterogeneous group. Disk displacement and osteoarthritis are the most common intra-articular abnormalities observed at imaging. As disk displacement is seen rather frequently in asymptomatic volunteers, it is a challenge to explain why disk displacement sometimes is symptomatic and sometimes is not. The present review focuses on abnormalities in the condylar bone marrow and the intra-articular soft tissues accompanying the disk displacement. The findings of temporomandibular joint in asymptomatic volunteers and in temporomandibular disorder (TMD) patients are reviewed. Both bone marrow edema and marrow necrosis are documented at histology and at magnetic resonance imaging (MRI) in TMD patients. Intra-articular soft tissue changes, such as synovitis, are additionally documented at arthroscopy. However, there is a controversy concerning which diagnostic imaging information is essential. Although there is no doubt that disk displacement and osteoarthritis may be accompanied by inflammatory alterations in the bone marrow and the intra-articular soft tissues, it has been difficult to consistently relate a specific imaging manifestation (bone edema, joint effusion, and synovitis) to joint pain. Longitudinal studies are needed to evaluate the importance of MRI abnormalities in the management of TMD patients.