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Temporomandibular disorders (also called TMD) affect the jaw and the muscles you use to chew and open your mouth. Often times, it is incorrectly referred to as TMJ, or temporomandibular joint, as this only refers to the jaw joint itself. There are several types of TMDs, each of which are discussed below.

The first type of TMD is masticatory muscle disorder, which involves the muscles responsible for chewing (scientifically referred to as muscles of mastication). About 45% of individuals with TMD have this type. The muscles responsible for chewing include the lateral pterygoid, the masseter, the temporalis and the medial pterygoid (see below pictures). When the masseter and/or temporalis muscles are involved, direct pressure of these muscles often reproduce pain. Additionally, mouth opening can be painful at end range and may be limited to less than 40 mm. If the lateral pterygoid is involved, pain at the outside of the jaw is often the chief complaint. We perform tests to see which muscle is involved. Masticatory muscle disorder can be caused through direct or indirect injury. Directly, this type of TMD can be caused through overuse or strain which occurs from gritting, grinding, clenching, bruxing, nail biting and/or gum chewing. Strain can also occur from overstretching that may occur during dental procedures, blows to the jaw or other microtrauma to the region. Indirectly, it can be caused through muscle guarding in response to TM joint inflammation, sinusitis, dental pathology or pain. Prolonged muscle guarding can lead to trigger points resulting in localized or referred pain to other areas including the ear, teeth or other areas of the face. Headache and vertigo may also result.

The next two types of TMD, disc displacements and joint dysfunction, involve the joint itself and can also be referred to as temporomandibular joint disorder collectively, or TMJD. There are two classifications within the second type: disc displacement with reduction, or DDWR, and disc displacement without reduction, or DDWOR. DDWR is the second most common TMD type with a click or pop occurring during mouth opening and a reciprocal click, sometimes muted, during mouth closing. This can result in excessive loading of the joint structures causing injury, inflammation and joint pain in the area just in front of the ear. Muscle guarding may or may not be present. It’s important to note that most people who have popping and clicking do not have pain or dysfunction demonstrating that the disc has the strong potential for healthy remodeling. While it’s possible DDWR may progress to DDWOR, most people with DDWR never progress to this. With DDWOR, mouth opening is now limited due to the inability of the jaw bone to glide forward. A history of jaw locking or catching is often reported. Like masticatory muscle disorders, disc displacements can happen from repeated microtraumas (i.e., gritting, grinding, clenching, etc.) causing excessive force on the joint resulting in thinning and displacement. Alternatively, disc displacement can happen from macrotrauma, which may occur from opening the mouth for dental procedures, intubations and blows to the face.

The last type is TM joint disorders related to joint arthralgia (joint pain), arthritis and arthrosis. Joint dysfunction may involve the temporomandibular disc, joint surfaces, joint capsule, ligaments, joint fluid or a combination of these structures. Often, disc displacements (the previously mentioned type) fall into this category as well as they may result in joint pain and/or functional motion restrictions. Osteoarthritis and osteoarthrosis also fall into this type. Osteoarthritis is the degeneration of the articular surfaces of the TMJ due to excessive loading and/or prolonged inflammation due to excessive parafunctional activities (i.e., clenching, grinding, etc.). Osteoarthritis is suspected if pain is present with a clicking or grinding feeling throughout the entire jaw joint movement. TMJ capsular adhesions to one side may also be present. If this is the case, mouth opening may be limited to less than 40 mm, limited lateral excursion to the opposite side, and protrusion with deflection towards the affected side. Arthralgia is present when there is pain with joint palpation (right in front of the ear) and end range movements.

Many patients have a combination of both masticatory muscle and joint disorders (displacement and arthralgia, arthritis and arthrosis). It’s important to mention all your signs and symptoms to your physical therapist to help determine the root cause of your TMD and whether or not to involve other practitioners in your care. This will help guide your treatment and determine to proper plan of care personalized to you

(Gauer & Semidey, 2015)
(Harrison et al., 2014)


  1. Gauer, R. L., & Semidey, M. J. (2015, March 15). Diagnosis and treatment of temporomandibular disorders. American Family Physician. Retrieved from https://www.aafp.org/afp/2015/0315/p378.html#afp20150315p378-f1
  2. Harrison, A. L., Thorp, J. N., & Ritzline, P. D. (2014). A proposed diagnostic classification of patients with temporomandibular disorders: Implications for physical therapists. Journal of Orthopaedic & Sports Physical Therapy, 44(3), 182–197. https://doi.org/10.2519/jospt.2014.4847

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