What conditions affect the TMJ
There are many conditions that can affect your TMJ, these are collectively known as Temporomandibular disorders or TMD. TMD can be broadly grouped into disorders affecting your muscles and dysfunctions affecting your TMJ.
Disorders of the muscles surrounding the TMJ (muscles of mastication) are the most common cause of TMD. Muscle disorders are associated with pain and dysfunction within the muscle and can cause a limitation to jaw movement. Muscle disorders can occur due to trauma, excessive or unaccustomed use of the masticatory muscles, excessive opening and stress. Other factors which may influence muscle function also include illness or viral infections.
Temporomandibular Joint Disorders
Functional disorders of the TMJ are extremely common. Often these disorders may not present with symptoms, instead with signs such as joint noises. These functional disorders of the TMJ can be broadly classified into three categories
• Derangements of the articular disc
• Structural problems with the TMJ joint surfaces
• Inflammatory joint disorders
Derangement of the articular disc
Derangement of the articular disc is due to an alteration of the attachment of the articular disc to the condyle. It is important to know the anatomy associated with the TMJ to fully understand the disorders that can occur. Please see anatomy section (LINK TO HOW DOES MY TMJ WORK).
• Disc displacement with reduction – this occurs when the disc is sitting in a more forward position on the mandibular condyle. When the mouth opens, the condyle relocates under the disc and is often associated with a click. When the mouth closes, the mandibular condyle moves from under the disc the disc returns to a more anterior position which is often associated with another click.
• Disc displacement without reduction – this occurs when the disc is displaced anterior to the mandibular condyle and cannot be returned to its normal position on the condyle. This disorder is always associated with a limitation in mouth opening as the condyle is unable to fully translate forwards on mouth opening as it buttresses against the displaced disc.
These videos explain the importance of the articular disc in normal and abnormal TMJ function:
Structural problems with the TMJ joint surfaces
Some of the disc problems already described can result from problems between the TMJ joint surfaces. In a healthy TMJ, the joint surfaces move smoothly over one another almost friction free and are lubricated with synovial fluid. Any disruption to the articular disc, cartilage covering the joint surfaces or changes to the lubrication of the joint will cause changes to the joint surfaces for example in osteoarthritis.
Inflammatory joint disorders
Inflammatory joint disorders are a group of conditions that affect the joints within the body including the TMJ. The specific joint structures become inflamed as a result of tissue damage or breakdown. Disorders that are included within this category are synovitis, capsulitis, discitis and inflammatory or rheumatoid arthritis. These disorders are usually associated with a constant dull ache which is usually worsened with mouth movement.