Over the last five weeks, I have been reviewing the vast library of literature that can be discussed in relation to the implications of temporomandibular joint dysfunction (TMJD) on athletic performance.
The majority of the evidence I have highlighted is related to studies looking at the effects of increased glial cell activation or increased substance P secretion. That said, whilst the research demonstrates that these factors can be caused by the hyper-sensitisation of the trigeminal nerve, many of the papers I have reviewed do not directly consider these effects in relation to TMJD.
For the main part, this absence of debate around the potential knock-on effects of TMJD are the reason I wanted to draw attention to this body of research & consider these links.
To take the next step towards evaluating the influence of TMJD on athletic performance, it is now important to understand what components need to be included in a thorough TMJ assessment.
Given that the potential causative factors for developing TMJD may be either dental, postural or psychological, the first decision we have to make as clinicians is, which members of our medical services & performance science teams need to be involved in the process.
Whilst TMJD has traditionally been the domain of the dentist, in my opinion, dentists, doctors, physiotherapists, osteopaths, dietitians, psychologists & conditioning coaches can all provide a valuable contribution to this process.
As with any assessment, a thorough, detailed subjective examination needs to be conducted, with valuable history gleaned around the onset (traumatic, post-dental intervention or insidious), psychosocial influences (anxieties, concerns, stress), congenital (genetic predisposition & maternal diet), dietary preferences & progression of signs & symptoms.
Objectively, it must be remembered that the articulation of the TMJ requires both joints to always move simultaneously. Therefore the objective examination must compare the alignment, muscle tone/bulk, as well as the amount/quality of the rotation & translation that occur at both left & right TMJ articulations during opening & closing.
Palpation over & around the joint itself at rest is important to detect the presence of any swelling or erythema (Meyer, 1990).
It is also important at this stage to palpate the masticatory (masseter, temporalis, medial pterygoid, lateral pterygoid) & cervical (sternocleidomastoid, trapezius, posterior cervical) muscles, where possible at the origins & insertions. This will involve some intra-oral examination, so have some latex-free surgical gloves to hand (excuse the pun).
Depending on your training, you can use this part of the examination to conduct any acupressure, trigger point or craniosacral assessments you employ too. My background in Thai massage leads me to work through the cranial, facial & cervical special points, which give me some valuable information as to the degree of neuromuscular involvement that has developed.
Following muscular palpation, the superficial temporal artery should be felt to assess for nodularity & discomfort.
Medical examination at this stage should include examination of the auditory canal & tympanic membrane with an otoscope, followed by tuning fork tests to eliminate aural pathology. If you suspect that the quality of hearing is being compromised, an audiogram would be advisable.
With regards movement, the TMJ should now be assessed through range during opening & closing as well as protraction & retraction of the mandible.
First of all, repeat the palpation whilst the patient executes those actions, being cognisant of the extent of mandibular condylar movement. You should feel the condyle move posteriorly as the jaw opens. If this elicits pain, it is likely that articular inflammation is present.
Using a stethoscope, repeat the movements with auscultation. A healthy joint should be relatively quiet during the movement, so the presence of crepitus, grinding, clicking or even popping sounds will suggest some dysfunction. For example, displacement of the intra-articular disc will cause a click or a pop to become audible during movement.
In respect of range, the degree of mandibular opening (distance between the incisal edges of the upper & lower front teeth) should be greater than 35mm in an adult. This is unlikely to exceed 60mm.
Observe the movement for any deviation from the midline through range, as muscle spasm or mechanical restrictions caused by a displaced meniscus will cause a shift to the side of pathology. In extreme cases, the jaw-in movement will “lock up”, as the disc blocks condylar translation, limiting the jaw opening to less than 25mm.
From a dental perspective, the quality of the occlusion, the term describing the contacts between the teeth, is an important guide as to the health of the TMJ.
Occlusion can be divided into “static occlusion” (the contacts between the teeth when the jaw is not moving), “freedom in centric occlusion” (the ability to slide slightly forwards before bumping into your front teeth) & “dynamic occlusion” (the contacts made between the teeth when the jaw moves sideways, forwards, backwards or at an angle).
Hassan & Rahimah (2007) detailed the various indices that are used to grade occlusion & malocclusion, suggesting that different methods have been developed to satisfy specific requirements.
A dentist will generally use articulating paper or occlusion foil to assess whether the bite is spread evenly over the back teeth & with greater pressure on the back teeth in comparison to the front teeth. However, the study by Carey et al (2007) investigated the assumed relationship between applied occlusal load & the area marked on articulating paper & was unable to establish a linear relationship.
The conclusion Carey et al drew was that the size of an articulating paper mark may not be a reliable predictor of the actual load content within the occlusal contact.
In light of this, there are computerised occlusal analysis systems available to dentists, that enable accurate & objective detection of teeth contact, biting time & force. These require patients to bite down on ultra thin sensors, whilst the data is recorded in real time & is analysed to construct a 3D representation of force distribution.
From a performance perspective, the influence of the occlusion quality on both proprioception & force generation are of interest. A friend of mine from Edinburgh that initially opened my eyes to the importance of jaw alignment in relation to performance metrics, a dentist named Iain Stewart, showed me an easy test that he regularly employs.
Iain uses either a one leg balance or elongated line stride to test proprioceptive deficits by comparing the quality of execution before & after correction to a neutral jaw position. The differences I have seen have been simply remarkable. There are several proprioceptive tests that have been shown to be valid & reliable, so it doesn’t matter which one is used.
From an S&C perspective, I think there is value in comparing 1RM or 3RM values for lifts that are relevant to your athletes before & after correction to neutral jaw position. Again, this is where collaboration between the dental professional & the conditioning coach becomes increasingly valuable.
The validity & reliability for this type of assessment has not been established & I have yet to see any studies that have examined such a comparison. However, it is my intention at some point in the future to do some studies in this area. If you have already beaten me to it, I’d be very interested in seeing the results.
If the initial objective assessment of the TMJ movement suggests a subsequent risk of TMJD, the aim is to establish whether any physical cause is intra-articular or extra-articular. Extra-articular disorders are more common, although some patients will demonstrate both intra- & extra-articular pathology concurrently.
Examples of extra-articular pathology are temporal arteritis, myofascial pain-dysfunction syndrome (MPDS) & psychopathology.
MPDS effects the muscles surrounding the joint, which results from sustained contraction of the masticatory muscles in response to stress or dental mal-alignment. Given the nature of potential causes of MPDS, sleep studies & psychological assessment might provide value to the examination in combination with dental assessment.
Often MPDS patients may be unaware that they are clenching, jaw thrusting or suffering from bruxism, which often will occur during sleep. These actions, when repeated for sustained periods, establish a cycle of pain & muscle spasm, which can then influence similar patterns in the cervical & cranial muscles.
Intra-articular conditions affecting the TMJ include dislocation, arthritis, ankylosis, meniscal disorders & tumours.
Dislocation may have occurred traumatically during a sporting collision, or somewhat more innocuously during eating, yawning, or through prolonged opening of the jaw at a dental appointment. When the jaw is opened to an extreme extent, the condyle translates forward, so it sits in front of the articular eminence, which can cause muscle spasm, causing the joint to become stuck in that position.
Any of the arthritic disease states may affect the TMJ in isolation or may present in association with a related presentation. In fact, it has been reported that 5% of people that suffer from some form of arthritis will go on to develop a TMJD. These cases will be apparent through crepitus detected during auscultation & many will go on to develop MPDS.
In the case of ankylosis, the joint may be fibrous or bony in nature & the result of either infection, rheumatoid factor, other arthritis or trauma. This presentation will likely restrict mandibular opening to 15mm or less.
Tumours of the TMJ are not common & will be associated with pain & restricted mandibular opening. Hyperplasia, osteochondroma, osteoma or sarcoma can cause enlargement of either the condyle or coronoid process, which will result in facial asymmetry & changes in dental occlusion.
The clinical examination of TMJD needs to be completed with imaging investigations & blood tests.
Magnetic resonance imaging (MRI) is valuable in depicting the presence of joint abnormalities & can therefore be considered a more useful modality than arthography or computed tomography (CT) in patients with internal derangements, chronic inflammation or suspected tumours (Larheim, 1995).
MRI has the ability to demonstrate abnormalities such as disc deformation, fragmentation & degradation, which indirectly suggests synovial proliferation. Larheim’s review reported a diagnostic accuracy of at least 90% in detecting disc displacements, with or without accompanying bony abnormalities when using oblique sagittal & coronal MRI.
A review by Larheim (2005) reported that in up to 80% of patients with TMJD referred for imaging studies, internal derangement was a significant finding on MRI in comparison with asymptomatic subjects. In addition, complete disc displacements occurred almost exclusively in the population with TMJD, despite this displacement not having a limiting effect on mouth opening.
MRI further detected joint effusion & mandibular condyle marrow abnormalities, such as oedema, in those diagnosed with TMJD, both of which were absent in the asymptomatic population. Laramie reported MRI findings related to joint effusion in just under 15% of TMJD patients, of which 30% demonstrated bone marrow abnormalities.
Interestingly, whilst the study by Larheim showed that disc displacement was mostly bilateral, the presence of joint effusion & changes in the bone marrow appeared to be predominantly unilateral. Pain was also either exclusively, or vastly greater, on one side as opposed to bilaterally & was positively related to the presence of effusion or condylar marrow abnormalities.
Osteoarthritic changes were only evident in a quarter of the joints with signs of effusion, whilst of those with more than just disc derangement contributing to severe intra-articular pathology, few had osteoarthritis.
In summary, the majority of patients referred to Larheim with TMJD demonstrated internal derangement related to disc displacement but did not have associated joint pathology.
CT is indicated in ascertaining more detailed information with regards to bone condition & soft tissue calcifications in joints demonstrating inflammatory diseases or tumours
Radiographs are useful in establishing the bony architecture of the joint & the position of the condyles during mandibular opening. For example, when differentiating between a hypo-mobility secondary to coronoid process enlargement & ankylosis
Lateral transcranial films display the anteroposterior contour of the bony joint structures, whereas transpharyngeal or transorbital x-rays best illustrate the anatomy of the mediolateral condylar.
Further medical investigations should screen for inflammatory markers in the blood that would indicate a potential systemic factor such as infection or rheumatic pathology. Conversely, establishing the substance P level is beneficial when trying to evaluate the effect of the TMJD systemically.
In summary, a thorough examination of TMJ movement & diagnosis of the causative factors of TMJD requires collaboration between several members of the multi-disciplinary performance science & medical services team. Subsequent management should be structured accordingly.
