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Examination: Joints

Examination: Muscles

Examination of the temporomandibular joint

Tenderness to palpation | Joint sounds | Range of motion

Range of motion

This is the only truly measurable parameter, as the others are more subjective. It is just as important to record jaw movement as a means to assess the rate and degree of improvement as it is to determine the severity of symptoms.

Movements to be measured are:

  • Incisal opening - pain free limit
  • Incisal opening - maximum (forced)
  • Lateral mandibular excursions
  • Mandible deviations on pathway of opening

Incisal opening

The incisal opening is measured from the upper incisal tip to the lower, with the patient first of all opening to the limit of their comfortable, pain free range. This is then compared to the normal range of motion (see right). Their maximum (forced) limit is also recorded. It is important to determine whether a limitation of vertical movement is due to pain or a physical obstruction. If it is pain, then it may be a muscular problem, if an obstruction, then disc displacement is most likely.

Lateral Excursions

The lateral movement should be measured from mid-line to mid-line, the patient moving the mandible to their maximum extent, from one side to the other.

Mandibular deviation

When the jaw is opened, the path it follows should of course be straight and consistent. Deviations from the norm are either lasting or transient, and are all suggestive of internal derangements of different sorts.

Lasting deviations

Lasting deviations are caused by the joint on one side not moving as far as on the other. If the movement is consistent but off centre(i.e. a straight diagonal pathway), this may due to adhesions within the joint. If the movement is normal till just before the maximum range, when a lateral deviation occurs, this may be due to anterior disc displacement without reduction (if the overall range of opening is reduced).


Jaw closed


Jaw opened

Transient deviations

Transient deviations occur when the joints are moving as far but at different rates. This is often caused by disc displacement with reduction.


Measuring the incisal opening

Normal Range of motion

Vertical

>40 mm

Male

>35 mm

Female

Lateral

>8 mm

Both sexes

Agerberg G
Swed Dent J
1974 67:81-86