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
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 Physical Therapist & Occupational Therapist to the suspicion that you are clenching or grinding your teeth in the night.
Degeneration
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.
Posture
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.
What Happens When You Lose Alignment Due to a Forward Head Posture, Such as While Using a Computer or Smart Phone?
- The head moves forward, promoting depression of the breastbone or sternum
- The cranium rotates posteriorly the first vertebrae (C1), promoting decreased space at the base of the skull and compression of the nerves and arteries that run through the upper neck and contribute to headaches
- As the heads moves forward, the mandible moves slightly back and change the TMJ articular disc position with the mandible/jaw bone
- A TMJ disc displacement problem may worsen over time, especially if one clenches in this position
- The curve of the cervical spine/neck will no longer be lordotic (curved inward), but change to a straight neck position that loads the neck joints and promotes slow progressive degenerative changes
- As the weight of the head hangs forward, the lower cervical spine bears the brunt of the weight and the fulcrum of C5-C6 region will flex and promote development of a dowager’s hump, osteophytes, degenerative disc disease, degenerative joint disease, narrowing between the joint spaces
- As the head is held forward, the muscles that connect the shoulders to the back of the head, such as the upper trapezius muscles, will bear the weight of the head and neck and develop tension and trigger points that contribute to pain in the head and neck
- As our heads are forward the pull of the muscles between the jaw bone and our sternum/breast bone will create tension which leads to clenching. Many of us are unaware of this and have facial tension all day long.
- Forward head posture causes the tongue in the mouth to move into a lowered position which reduces our airway support and leads to a decreased amount of space in our throat for breathing and eventually causes snoring in patients during sleep.
Other Causes
TMJ disorder or TMD joint-related pain may be caused by trauma, such as a blow to the face, fall on the chin, or a car accident. A history of trauma can increase risk for arthritis. Clenching or bruxism and neck tension also are known to increase TMJ pain and compression, which can also aggravate arthritis.
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.
How Does Being Hypermobile or Loose-Jointed / Double-Jointed Affect My TMJ?
Patients who are hypermobile throughout their bodies, are “double jointed” or loose-jointed can develop pain in the TMJ due to over-stretching of the jaw. The connective tissue and ligaments surrounding the TMJ are looser than normal may create problems with stability of the TMJ. These patients tend to have difficulty tolerating dental work and can even have problems dislocating or subluxing the TMJ. If a patient is told that he/she has systemic hypermobility, learning proper head-on-neck posture and exercises to stabilize the jaw can help prevent these issues. Our therapists can help you learn the limits of mouth opening when hypermobile so as not to overstretch the joint and cause instability. Repeated opening past the stable joint position can lead to disc displacement. Our specialists utilize manual therapy techniques to reduce TMJ disc displacement and reduce joint noise and clicking.