The jaw/core relationship
Jaw pain and clicking jaws can be a symptom of headaches, low back pain, neck pain.
Author: Michael Hobbs
What I’ve been seeing a lot lately in clinic is relationships between jaw (also known as the TMJ joint) and core dysfunction. Typically, it’s an overactive jaw compensating for an underactive intrinsic core, although I’m sure the opposite is also possible (just not something I have personally found).
Of course, patients don’t come in telling me they have a jaw/core dysfunctional pattern. They will come in complaining of low back pain or neck pain or headaches. And when I question further, they often do tell me about jaw clenching or teeth grinding or something of the sorts. Sometimes it’s whilst they are at work, sometimes it’s at night, sometimes it’s at the gym. And when I examine their jaw, they often have a significant lateral deviation of the jaw, the jaw deviating to one side, either during opening or closing of the jaw. They tell me they sometimes click their jaw when they get stressed or that it’s been doing this grinding thing for years and years.
If this deviation goes unchecked, it can lead to chronic jaw issues or predisposition to injury elsewhere in the body. The swing is created by the lateral pterygoid on the opposite side and the temporalis on the same side of the swinging jaw. The lateral pterygoid muscle attaches to the joint capsule and the articular disc (yes, you have a disc in your jaw, which separates each side of your jaw joint into 2 joints: an upper and a lower joint). Over time, this can distort the shape of the disc and cartilage, leading to a painful click as you open or close your jaw. However, very often, we find that it is the side of the jaw that moves too much that is the painful side. Very commonly they also have a jaw overworking for a lack of intrinsic core stability. It seems like magic. But what is the real connection here?
Your jaw develops from the first branchial arch, a collection of arches which develop from your voicebox (which, at that stage, is still part of your primitive gut), which begins developing around the 4th week of development, from when you are still more similar to a fish than a fully-developed human (similar arches become the gills in fish). It is from old parts of your brain, the brainstem, that have developed to function at a reflexive level, long before there is any conscious awareness or control of what is happening.
In modern day humans, jaws become so dysfunctional because of this old circuitry. Many of us clench without even realising, because old circuitry is involved in reflexes, and work at such a subconscious level. This is also why it can be so hard to actually treat and fix bruxism (jaw clenching and grinding): in order to fully treat jaw clenching, you seriously need to address some very subconscious patterns that are wired in deep.
The trigeminal nerve (the nerve that supplies the jaw) provides the brain with the head’s proprioception (proprioception being your body’s ability to detect where it is in space). There are a huge amount of muscle spindles in your jaw muscles, which detect stretch and tell the brain and the rest of the body how you are standing and moving.
In other words, the nerve to your jaw is what helps keep your eyes level and maintain posture and stability. It finishes in the sensory trigeminal nuclei, which extend through the whole of the brainstem (what we call the pons, the midbrain and the medulla oblongata) and even into the upper cervical spine. These nuclei are literally an extension of the sensory highways of your spinal cord, that run all the way down to your tailbone, and provide sensory feedback from the rest of your body up to your brain.
It is very important for you as an organism to be able to know where your head is in space. If you weren’t able to do that, you’d surely have given yourself brain damage by now from the number of times you’d bumped your head walking into things, you’d definitely have eye problems from not knowing you were walking around with your eyes not even level and you would most likely be suffering from constant, unremitting vertigo. The trigeminal nerve sends lots of information to your vestibular system, your balance system, which is why people with jaw syndromes often also complain of dizziness or hearing symptoms.
So the role of this trigeminal nerve becomes kind of important. And how you hold your head affects everything below it. Try this now. Close your eyes and shift your jaw to the left and then to the right. If you pay close attention, you may notice that the sensation is that your entire body has shifted in the opposite direction. That is, if you shift your jaw left, your entire body feels as though it has shifted right; and if you shift your jaw right, your entire body feels as though it has shifted left. We forget that posture is also subconscious- it is a reflex! It’s how our body automatically organises itself. And if your body is trying to shift your pelvis left and right, which is does with every step that we take when we are walking and running, it may get confused and shift your jaw instead of your pelvis.
For most of us with dysfunctional jaw/core relationships, we have a tendency towards favouring our jaw shifting to one side more so than the other. This tends to be the side that the jaw will swing to when it is opening or closing. In this position, our core tends to test strong. However if we swing the jaw the other way, the way we are less familiar with, the core tends to then test weak.
In other words, we compensate by over-activating our jaw one way to make up for a lack of tension elsewhere in the system (usually in the core or pelvis) to give our brains the sensation of stability. And when I take away that compensation strategy for you, by making you shift your jaw the other way, it makes the dysfunctional pattern incredibly clear, as you can no longer rely on your jaw muscles to stabilise you.
The reason we over-clench is because it works! Studies estimate that by clenching your teeth during things such as weight lifting, your strength will increase by up to 10% without having to do anything else. We also know a lot of powerlifters crack or grind their teeth when they lift, so that they wear mouth guards, for this very reason.
Whilst that may be an effective hack in the short-term, I wouldn’t recommend making it a training strategy. It doesn’t help at all with any movement tasks that require precision, such as golf. And it’s tricking your brain into thinking it has permission to do something by creating a false sense of stability or movement. I generally believe most people should keep the face and neck as relaxed as possible when they exercise. Everything below the neck down can be tense, but the face shouldn’t be. So you can use teeth clenching as a quick hack to get stronger; however I would argue that most of us are subconsciously doing this all the time already. A lot of us are already carrying way too much tension in our neck and jaw. Perhaps what we need instead is less clenching and more core stability.
References:
https://www.ncbi.nlm.nih.gov/pubmed/27003454
https://www.sciencedirect.com/science/article/pii/S2352587817300098
https://www.sciencedirect.com/topics/medicine-and-dentistry/functional-anatomy
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4451241/
Date Published: 31 October 2021