Patient-friendly definition from the DentistsDirectory.org dental glossary.
The temporomandibular joint (TMJ) is the hinge-and-glide joint that connects the mandible (lower jaw) to the temporal bone of the skull, located just in front of each ear. There are two TMJs, one on each side, and they work in tandem with the muscles of mastication to enable the complex movements of chewing, speaking, and swallowing. TMJ disorder — more accurately called temporomandibular disorder (TMD) — is an umbrella term for a group of conditions producing pain and dysfunction in this joint and the surrounding muscles.
TMD produces a characteristic cluster of symptoms. Jaw pain is most common, typically felt in front of the ear and radiating into the temple, cheek, or neck. Clicking, popping, or grating sounds from the joint when opening or closing the mouth are common — these sounds (called crepitus) result from the articular disc inside the joint shifting position. Limited jaw opening (trismus), the jaw deviating to one side when opening, difficulty chewing firm foods, and earache or fullness are also common. Because TMD often co-occurs with headaches, neck pain, and shoulder tension, it can be mistaken for other conditions.
The good news is that the majority of TMD cases resolve or significantly improve with conservative, reversible, non-surgical treatments. These include: occlusal splints (nightguards) to reduce muscle overload and protect the joint during sleep; physical therapy to improve muscle and joint function; anti-inflammatory medications; applying warm or cold compresses; dietary modifications (soft foods during flares); and stress management to reduce bruxism and clenching. Surgery is reserved for severe, unresponsive cases and is performed by an oral surgeon or TMJ specialist. Irreversible treatments like extensive bite adjustment are rarely indicated for TMD and should be approached with great caution.