A single specific cause of TMJ pain can often be difficult to discern as it is frequently due to a combination of factors affecting the joint.
Congenital jaw anatomy
Congenital jaw anatomy means the anatomy that you were born with. The unique variations in jaw size, jaw resting position, and the position of your teeth once they grow in (including the adult wisdom teeth) can affect the wear and tear on the TMJ. In most cases anatomy alone does not cause TMJ issues but rather your individual anatomy in combination with other mitigating factors, can results in TMJ pain.
Trauma can be in the form of a single macrotrauma to the joint (or related anatomy) or many little microtraumas to the TMJ. Macrotrauma to the TMJ may include injuries such as a punch to the jaw, a jaw fracture, a dislocation of the jaw, or even a motor vehicle accident. Microtrauma, such as prolonged opening of the mouth while receiving repetitive dental treatment, or repetitive gum, nail or pen chewing over time can also lead to TMJ pain. Trauma, both macro and micro, can disturb the normal alignment of the TMJ, cause tension in the muscles controlling the joint, and lead to abnormal wear on the articular disc.
Bruxism (Teeth Clenching & Grinding)
Clenching and/or grinding of the teeth are also considered forms of microtrauma to the TMJ. Many people clench their jaw as a habit, particularly when stressed. Repetitive chewing such as on gum, a pen, or on your nails is also a form of repetitive clenching. Clenching causes recurring stress on the ligaments and disc and also increases tension in the muscles of the TMJ, all of which can lead to pain in the joint.
Teeth grinding is most often a habit that occurs at night. In some cases, the grinding is so intense that it heard by others sleeping in the same room. Intense grinding can cause wear down of the teeth and in severe cases can actually break teeth, fillings or crowns. Some cases of grinding may be mild and not cause any notable symptoms at all in the TMJ. As with repetitive clenching, the excess force creates undesirable stress on the TMJ. Often TMJ pain that is worse upon waking leads your physiotherapist to the suspicion that you are clenching or grinding your teeth in the night.
All joints wear down over time due to the natural process of aging, and the TMJ is no exception. In some cases, this wear and tear (osteoarthritis) occurs earlier than normal or is amplified by trauma, other biological factors, or inflammatory disease processes. Wear and tear can lead to pain in the joint.
Prolonged poor neck (cervical) posture can directly affect the TMJ due to the close anatomical proximity of the two areas. The most common posturing fault that is seen in relation to the neck is a forward head position. Normally when the neck is in good posture and in line with the rest of the spine, a plumb line seen from the side of the body falls through the ear lobes and the middle of the shoulder joints. Many people, however, naturally rest their head with their chin poking forward. This results in the plumb line from the ear lobe falling out in front of the shoulders, and the weight of the head falling in front of the body. Computer or desk workers commonly display this neck posture. This forward head posture not only increases the stress on the neck, but also affects the position of the TMJ by dragging the lower jaw forward and in effect creating a constant shear and pressure of the TMJ condyle and articular disc towards the front of the joint.
Other non-orthopaedic problems can cause or contribute to TMJ pain. Patients suffering from chronic pain disorders such as fibromyalgia or systemic disorders such as rheumatoid arthritis commonly feel pain in their TMJ. Psychological stress alone can also lead to TMJ pain, as can other more sinister problems such as tumours. In addition some ear, nose and throat problems can also manifest in TMJ pain, therefore a thorough examination is required to determine any contributing factors and also to rule out any serious issues.