What Is the Temporomandibular Joint (TMJ)?

The temporomandibular joint (TMJ), or jaw joint, is a synovial joint similar to the knee or hip and connects the lower jaw to the skull (temporal bone). It is located directly in front of the ear. This joint is responsible for moving your lower jaw during chewing or talking.

Each person has two TMJs, which are connected by one lower jaw. Additionally, the TMJ itself has a meniscus, or disk, which is made of fibrocartilage instead of hyaline (knee) cartilage. It partially comes out of the socket during normal function, allowing for maximal opening.

Temporomandibular Joint Disorders

Temporomandibular joint disorders are a common musculoskeletal problem, second only to chronic lower back pain. These disorders are divided into conditions affecting the muscles (link to muscle disorders) around the joint and diseases affecting the bone and cartilage of the joint. The most common diseases affecting the TMJ include:

  1. Myofascial temporal mandibular disorder, also known as myofascial pain syndrome, which is caused by tension, fatigue or spasms in the masticatory muscles
  2. Internal derangement of the TMJ, which is a disruption or displacement of the disc within the joint

Often these two conditions occur together. In most people, pain and dysfunction is brief.  

Treatment with a short course of conservative medical management results in a favorable outcome; however, some people have a more aggressive disease state requiring additional treatment. 

TMJ disorders often cause similar symptoms and may mimic chronic headaches, sinus or ear disease, neck or tooth pain. Evaluation - including medical history, exam, imaging and lab work - by a physician and dentist will help to determine the correct diagnosis and treatment course for you.

Types of Conditions that May Affect the Temporomandibular Joint

Because muscles and ligaments are responsible for the movement of this joint, any problems around the joint may also cause pain or difficulty opening. Some of the conditions that may affect the joint include:

Osteoarthritis

Osteoarthritis (OA) is also known as degenerative arthritis, degenerative joint disease, or osteoarthrosis.  This joint disease results from breakdown of joint cartilage and underlying bone.
 

Jawbone Infections

Jawbone infections can be caused when a dental cavity remains untreated, a tooth has been extracted or from other dental procedures. If an infection is not properly treated it can travel into the jawbone and cause serious health issues. 

Symptoms of a jaw bone infection or dental abscess include pain in the mouth or jaw. 

Mouth and Jaw Tumors

Both benign and malignant tumors can be found in the mouth and jaw. Symptoms are swelling, pain, tenderness, and unexplained tooth mobility.

Rheumatoid Arthritis

The jaw joint can be impacted by rheumatoid arthritis much like it impacts other joints in the body with inflammation, bone erosion, and tissue damage.
 

Post-Traumatic Arthritis

Post-traumatic arthritis is a common form of osteoarthritis (OA) that is caused by a previous injury or other form of trauma. (Osteoarthritis is the wearing away of cartilage in the joint.) 

This condition can occur in any joint, including the jaw. 

Tendonitis

Past injury, trauma and changes to the bite of the teeth can contribute to painful symptoms of tendonitis. Pain may be felt at the ear, temple, eye, cheekbone, below the lobe of the ear or at the jaw joint.

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