There are two types of joint sounds: clicks and crepitus. Clicks are single explosive noises that likely represent sudden distraction of wet surfaces, indicating disc displacement. Crepitus is a continuous grating noise caused by worn joint surfaces, common in degenerative joint disease. Determining if a click occurs during rotation or translation helps locate whether the disc is displaced medially or laterally. The temporomandibular joint rotates during the first half inch of opening and translates thereafter, so noises during rotation indicate medial disc displacement, while noises after translation begins indicate lateral displacement. Doppler auscultation allows differentiation between rotational and translational noises to accurately locate the site of disc displacement.

1. Joint sounds
There are 2 types of joint sound to look out for:
• Clicks - single explosive noise
• Crepitus - continuos 'grating' noise
Clicks
A joint click probably represents the sudden distraction of 2 wet surfaces, symptomatic of some
kind of disc displacement. The diagnosis of a joint click, and therefore treatment, varies on
whether the click is left, right or bilateral, painful or painless, consistent or intermittent. The
timing of a click is also significant: a click heard later in the opening cycle may represent a
greater degree of disc displacement.
Clicks may frequently be felt as well as heard, though they are not normally painful.
Crepitus
Crepitus is the continuous noise during movement of the joint, caused by the articulatory surfaces
of the joint being worn. This occurs most commonly in patients with degenerative joint disease.
The joint sounds should be listened to with a stethoscope, preferably a stereo one, as the two sides
can be more easily compared.
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.

2. 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.
Medial or Lateral Pole?
Occlusion/TMD
Sep152011

3. I’m not sure of the exact percentage of patients that have a “pop” or “click”,
but joint noise is a common finding. When working with a patient that has joint noise my
primary concern is to assess the stability of the joint. If the situation is unstable or the patient
is symptomatic relative to the joint, then together we determine the appropriate treatment to
try to establish an asymptomatic, stable condition. Other patients who come to see me with
joint sounds are asymptomatic, and from my examination have a stable joint. The next
question I ask myself, especially if they have restorative concerns, is “what is the risk of
altering that stability”?
Checking for Palpable Sounds
Regardless of whether I am trying to answer the question of stability, or determine a course
of treatment, one question must be answered, where is the disc? A more accurate way to
ask the question is really, “Where is the disc off?” There are only two choices, medial pole or
lateral pole, but knowing the answer is a key piece of information. Taking a thorough history
is an important piece of understanding the health and stability of the joint, and begins to point
us towards our answer. The definitive answer comes from analyzing the joint sounds and
determining whether they occur in rotation or translation. When the temporomandibular joint
is seated the load from the muscles is delivered through the medial aspect of the head of the
condyle and disc. This load remains on the medial aspect during rotation and begins to move
laterally as the joint opens further and begins to translate. Rotation occurs during
approximately the first 1/2 inch (12mm) of opening, after that the joint is translating until it
reaches maximum opening, and then the process reverses. During lateral excursions, the
working joint (right lateral the right joint) is rotating and the non-working or balancing side is
translating.

4. Doppler Auscultation
With this ability to differentiate when rotation is occurring versus translation, all we have to do
is record during which movement the noise occurs. If the pop, click or crepitus occurs during
rotation, the disc is displaced on the medial. If the noises occur after translation has begun,
the displacement is at the lateral aspect. Pops and clicks can often be detected with joint
palpation and this is always part of my exam, but in order to not miss crepitus or noise that
isn’t palpable I auscultate. thedoppler will pick up noise and let me easily differentiate when it
is occurring rotation (medial) or translation ( lateral), it also allows the patient to hear the
noises and get curious about what it means.