Posted on 18 Oct 2010 15:27
By Ground Up Strength
The masseter is a jaw muscle that gets its name from the Greek work "to chew". It is the major muscle of mastication (chewing) of the human jaw and serves primarily to elevate the mandible (lower jaw) while the deep tissues help to protrude (protract) it forward. Although we rarely think of it, the mandible is the only bone of the skull that is actually moveable. The upper jaw is fixed. There is a lot of moving for the mandible to do, therefore, and the masseter is the primary worker. Located on each side of the face in the parotid1 region at the back of the jaw, these muscles are easily visible or palpable when you clench your jaw, as they contract strongly just in front of the lower ears.2
The masseter muscle covers the side of the jaw nearest the ear and for its size it is one of the strongest muscles and some physiologists believe it to be the strongest muscle of all but this is hard to determine with complete accuracy.3
The average human can bite down with a force of 150 pounds and bites of over 250 pounds are within the norm. In fact the world record bite recorded by the 1992 Guinness Book of Records records the strongest human bite at an astounding 4,337 N or 975 foot pounds for 2 seconds. The masseter achieves these seemingly impossible forces because of its mechanical advantage as it its lever arm is much shorter than most muscles.
Masseter Muscle Origin and Insertion
Origin: The larger superficial layer originates on the zygomatic process of the maxilla and the lower border of the zygomatic arch. The smaller deep portion originates on the zygomatic arch.
Insertion: The superficial portion inserts on the ramus of the mandible and the deep portion inserts on the upper half of the ramus and the lateral surface of the coronoid process of the mandible.
Masseter Trigger Points and Referred Pain
The masseter muscle can easily become chronically tense with trigger points and it is the most likely muscle to cause severe problems with opening the jaw. As mentioned above, the muscle is highly active and is among the first to tense when we are in emotional distress or when we are concentrating deeply or angry. This tension can go on for extended periods of time so that the masseter is likely to be a problem at some point for almost everyone. Clenching or grinding the teeth in this fashion is called bruxism and it happens to all of us once in a while. For some this can become a chronic and debilitating problem, especially when it occurs during sleep as part of a sleep disorder. The masseter and other muscles of mastication can suffer tremendous strain and develop trigger points. On the other hand it is possible for the presence of trigger points in these muscles to bring on bruxism.
Trigger points in the superficial layer can refer pain to the eyebrow, upper jaw (maxilla) and the rear part of the mandible. They can also refer pain to the upper and lower molars which can become sensitive to pressure or temperature change so when the molars suddenly become sensitive check the masseter for trigger points before you buy special toothpaste for sensitive teeth or visit the dentist, although it is always best to seek professional medical advice when experiencing any kind of unusual pain or discomfort. Trigger points in the deep layer refer pain to the ear region (see images below).
In general, masseter trigger points cause pain in the eye, face, jaw, and teeth area. An unexplained earache can be a result of masseter trigger points and it is reported in Travell an Simons that TrPs of the masseter can even cause that annoying itch deep in the ear that you can never quite scratch. Trigger points in the deep layer may also be a cause of tinnitus (perception of ringing noise in the ear with no cause)4 They are a possible contributer to myogenic tension type headaches especially if TrPs of the neck muscles are contributing to the headache pain.
Superficial and Deep Masseter
Forward head posture can cause problems leading to trigger points in the masseter. This posture indirectly causes tension in the supra and infrahyoid muscles which in turn pull down on the masseter lightly. In order for trigger point therapy of the masseter to be successful, posture must be corrected. Since associated problems may involve many muscles it may be best to see a professional therapist, but in general, correction of posture should help alleviate myofascial pain of masseter origin.
If the masseter develops trigger points its synergists are likely to follow suit, so expect TrPs in the temporalis and medial pterygoid muscles. It is associated, with TrP's of the neck and jaw muscles, with TMJ pain and bruxism. Headaches and TMJ pain may likely be caused by complex overlapping referred pain patterns by several muscles of the jaw and neck, such as the sternocleidomastoid, which is associated with forward head posture, or the trapezius.
Masseter TrPs may often be satellite5 trigger points to primary trigger points in the larger neck muscles, such as the trapezius. The masseter and temporalis are posture muscles controlling the position of the jaw (the temporalis does most of the job during relaxation) and they control the position of the jaw during chewing. Since the head always moves during chewing as well the neck muscles and the mastication muscles are linked in postural control. Therefore it can be difficult to alleviate trigger points in the masseter (and temporalis and pterygoid) if there are trigger points present in the neck muscle. The reverse is also true.
Masseter Trigger Point Self Treatment
As you can see from the images below, trigger points can develop any where on the masseter muscle including near the cheek bones, and the bottom edge the jaw. They can be massaged from the outside with with the fingers being supported by the opposite hand but the best way is to put your thumb inside your mouth and knead the muscle between your thumb and fingers. Using the hand opposite from the side you are workng on, insert your thumb back in front of the molars the molars and feel for the bony ridge-like area called the coronoid process. This is the area to work on and you should be able to feel the thick and rubbery masseter muscle. Press the muscle between the thumb and the index and middle fingers.
Explore the muscle from the top to the bottom and all the way back to the ear. Find the most tender areas. The images below will give you an idea of where to expect the tender points. Pressing on and massaging these points may feel very painful. Massage them as strongly as you can stand for about one minute. Continue daily until the pain and problems subside and squeezing the muscle no longer hurts and then continue for several days after that.
Masseter Trigger Point Images
Masseter attachment trigger points near the upper
musculotendinous junction of superficial layer and
central trigger points of superficial layer with
referred pain patterns to lower jaw, teeth, and
Masseter attachment trigger points of the lower
superficial layer with referred pain patterns to
lower jaw and above eyebrow.
Masseter trigger points of the upper posterior
deep layer below temporomandibular joint
with referred pain patterns to ear area.
This "Sternocleidomastoid Muscle: Location, Action and Trigger Points" page is provided by Ground Up Strength for information purposes only and should not take the place of professional medical advice. Although we have done our utmost to provide accurate and safe information, we are not medical professionals and the information on this page should not be taken as professional medical advice, or any other kind of medical advice. Any self-treatment undertaken by you is undertaken at your own risk.
Unless otherwise noted, all images on this page used under license. Images by LifeART (and/or) MediClip image copyright 2010. Wolters Kluwer Health, Inc.- Lippincott Williams & Wilkins. All rights reserved. Images not for reuse.
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This page created 18 Oct 2010 15:27
Last updated 23 Feb 2015 20:07