Fascia and Pain
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To be honest, this is a huge topic bearing in mind that pain science is complex and multifactorial on its own. As most fascia research is still very new, it is very likely that we are only aware of the tip of the fascia iceberg. While we do have some research into fascia’s role in pain, there is probably so much more to learn.
In my recent social media posts, I have focused on hyaluronan (HA), fascia densification, thoracolumbar fascia and pain. I also presented an online master session specifically on the thoracolumbar fascia at the end of 2022 which if you haven’t seen, you can still purchase the recording here.
I’m going to try and give you a resume of the main points of the items I've just mentioned which I feel are the most logical order so that you can use this information immediately in your clinical practice.
Firstly, HA is a molecule in fascia’s ground substance which you may know as the extra cellular matrix. The ground substance mostly surrounds the fibres of the loose connective tissue which separates areas, or layers, of dense connective tissue. Both loose and dense connective tissues are considered deep fascia. Think of two slices of bread being the dense connective tissue and the jam in between being loose connective tissue. Simply because of the jam, the two slices of bread can somewhat glide past or over each other. This is the responsibility of HA. HA modulates the fluidity, or gel state, of the ground substance because it is a molecule which attracts water molecules to it. The more water molecules HA attracts, the more fluid or gel like the ground substance becomes.
However, when there is less water content, this fluid or gel state becomes thicker increasing in viscosity. When there is increased viscosity, the surrounding tissues are not able to glide past each other and the tissues essentially become less mobile. This state is what Drs Antonio and Carla Stecco, researchers from the University of Padua in Italy, call densification.
Densification is different to fibrosis according to the Steccos. Densification if left untreated, and by that I don’t mean manual therapy necessarily, but resolution from restoration of movement, stress reduction and lifestyle changes, may result in fibrosis. Fibrosis is where both the loose and dense connective tissues are affected with an increase in collagen that would need on-going regular rehabilitation and for some, may not be possible to resolve. Densification on the other hand can be somewhat short-lived and may resolve naturally overnight and is something that we as manual therapists may be able to affect with hands-on or tool therapy (Pratt 2021) and (Parvan et al. 2014). While there are hypotheses and suggestions on how manual therapy and MFR may affect tissue, there is still uncertainty. However, there is potential in the ability for manual therapy to alter the viscosity of the ground substance and this is currently being researched.
If fascial structures are not able to glide past or over each other, this could contribute to what we feel under our hands as the pull and drag of the tissues. This may also be an explanation for the sensation that the client experiences when they have lack of movement and even pain on movement. However, having to accept the fact that none of us have x-ray vision, this is purely conjecture but anecdotally makes sense.
Additionally, as the tissues have less glide, this may compromise the sensory nerve endings which discriminate load. Potentially, additional pressure may cause them to alert the brain to potential tissue damage resulting in the experience of pain. There may also be an altered chemical environment due to a decrease in blood and oxygen supply which may again stimulate these sensory endings, called nociceptors, to alert the brain to potential tissue damage resulting in the experience of pain.
The thoracolumbar fascia (TLF) is a tissue structure spanning the area from your pelvis to your neck. It is made of 2 to 3 layers of tissue all being pulled into a tight span across your back by its surrounding muscles. The TLF is responsible for load transfer between your upper and lower body and also provides stability to the spine. When any of the muscles which hold the TLF into tension are not performing their job correctly, it creates a cascade affect across the entire TLF resulting in lack of function and stability, uncoordinated gait, poor range of motion and even pain.
Finally, we come to pain. It has been identified that the TLF is innervated by many different sensory receptors many of which are responsible for advising the brain of potential tissue damage, called nociception. It is important to understand here that pain does not travel through nerves; there are no pain nerves. Nociception is the ability of the body to identify any sensation be it chemical, thermal or mechanical which may be potentially damaging or noxious. A research study was completed where individuals had the fascia of their low back injected with hypertonic saline solution which is an irritant. Each participant indicated the experience of pain as a result (Shilder 2014). There have been further studies where nerve endings that sense potential tissue damage (nociception) have also been identified in the tissue surrounding the hips (Fede et al. 2020).
Almost every tissue in the human body is embedded with sensory nerve endings. It is not only exclusive to the skin. Interestingly, the brain and spinal cord don't have nociceptors. Can you work out why?
It is now commonly accepted that the fascial tissues have sensory receptors including free nerve endings, sometimes called interstitial nerve endings, which sense chemical, thermal and mechanical changes as well as sensory inputs that are potentially dangerous or damaging (noxious) to the body.
Fascia may play quite an important role in the experience of pain from a mechanistic point of view. However, as I said previously, pain is complex, and pain can be experienced in the absence of a tissue issue. Therefore, it is of vital importance that you understand the complex nature of pain to the best of your ability so that you can continue to help your clients with the most evidence informed practice possible.
Background photo header pic: © Fascia Research Society. Photography by Thomas Stephan.
Pratt RL. Hyaluronan and the Fascial Frontier. International Journal of Molecular Sciences. 2021; 22(13):6845. https://doi.org/10.3390/ijms22136845
Pavan, P. G., Stecco, A., Stern, R., & Stecco, C. (2014). Painful connections: densification versus fibrosis of fascia. Current pain and headache reports, 18(8), 441. https://doi.org/10.1007/s11916-014-0441-4
Schilder, A., Hoheisel, U., Magerl, W., Benrath, J., Klein, T., & Treede, R. D. (2014). Sensory findings after stimulation of the thoracolumbar fascia with hypertonic saline suggest its contribution to low back pain. Pain, 155(2), 222–231. https://doi.org/10.1016/j.pain.2013.09.025
Fede, C, Porzionato, A, Petrelli, L, et al. Fascia and soft tissues innervation in the human hip and their possible role in post-surgical pain. J Orthop Res. 2020; 38: 1646– 1654. https://doi.org/10.1002/jor.24665