Takeaway: Whenever two surfaces need to glide—like tendon sheaths, the pericardium and the heart, or two muscles along each other—hyaluronic acid ensures everything goes smoothly.

First, let’s all get the pronunciation of this five-syllable word—hyaluronan—down 100 percent: Hi-ah-lu-ROH-nan. More conventionally, it is known as hyaluronic acid (HA). 

A simple search on the web reveals thousands of videos about the benefits and the hype surrounding HA related to dermatology and skin care. Being a hydrophillic, water-loving molecule, HA is often added to skin care creams to restore and retain moisture. It’s also an additive to massage oils and creams. Hyaluronic acid is readily available as a supplement, though there doesn’t seem to be any solid evidence about the benefits of taking it orally.

Hyaluronan does play a number of other, non-skin care roles in the body. To highlight a few, HA acts as a shock absorber in the synovial fluid, a space filler in the aqueous humor of the eye to provide tissue turgor (elasticity), and as a cushion against vascular compression in the connective tissue of the umbilical cord. What is of most interest to us as manual therapists is its role in lubrication. When two surfaces need to glide—like tendon sheaths, the pleura between the lung tissue and the interior wall of the chest cavity, the pericardium and the heart, or two muscles along each other—HA makes sure everything goes smoothly. Essentially, hyaluronan is the WD-40 of your body.

Since HA is found throughout the body, many types of cells are capable of producing it, including fibroblasts, synoviocytes, smooth muscle cells, and the cell we want to focus on: the appropriately named fasciacytes. 

Fasciacytes

First discovered by a group of researchers including Antonio and Carla Stecco, the fasciacyte was described as being “fibroblast-like.” Despite the similarities, it was determined that the fasciacyte differed enough in both structure (it’s much plumper) and immunoreactivity to be classified as a new cell type. That’s kind of a big deal. This discovery and its relevance was first published in 2011 in Surgical and Radiologic Anatomy. However, this new knowledge did not become more widely known until late 2018, when a follow-up paper titled “The Fasciacytes: A New Cell Devoted to Fascial Gliding Regulation”was published in Clinical Anatomy, which made it a much bigger deal.¹ 

What’s important about fasciacytes is what they do and where they live. What they do is secrete hyaluronan. And where they live is in the outer layer of loose connective tissue that serves as an interface between the deep fascia and the epimysium of the muscle. The fasciacytes produce the HA that allows for smooth sliding and gliding between muscle and fascia, and likewise along the muscle and fascia of its adjacent neighbors. Think of the hamstring or quadriceps groups. It goes deeper than that, allowing the perimysial bundles to slide and individual muscle fibers to glide in their fascial, endomysial sheaths. 

When it goes wrong, the HA gets thicker and sludgier and becomes more adhesive. Things don’t slide well. This is called densification. It can happen for any number of reasons, including elevated pH levels, overuse syndromes, injuries, and surgeries. Densifications tend to lead to compensation patterns. They can also lead to myofascial pain. And long-term, it can lead to fibrosis.

Something else that is abundant in the sliding interface between the muscle and fascia are sensory nerves, particularly type IV proprioceptive nerve endings. When these nerves can no longer enjoy a smooth ride along their immediate fasciomusculoskeletal environment, they are trapped by a densification. And those nerve endings are going to tell you about it, most likely by generating a pain signal. The automatic response is to avoid moving that area, which will only serve to increase the densification—and cause more compensations. This should lead us to think about different strategies for treating entrapment syndromes.

Motion is Lotion, Literally

Fasciacytes love shearing motions. When things are moving and grooving, that keeps them pumping out the HA we need to stay sliding and gliding, lubricated and happy. As far as we know, this isn’t something you can get by taking hyaluronic acid supplements. Therapeutically, fasciacytes respond to pressure and perpendicular, shearing motions as opposed to long, sliding strokes. This response can change the viscosity of the HA, making it less dense. Mechanical perpendicular vibration (using mechanical vibrators and the like), as well as rapid back-and-forth motions (tangential oscillation) with the knuckles can engender this effect, with the latter approach having recently been shown via imaging to increase water content around the areas of densification.

I often use the outside edges of my hands (or a concert of fingertips) like a wedge between epimysial divisions of particular muscles (at least, that is my therapeutic intention) while simultaneously engaging in rocking and/or oscillatory motions to root out and
de-gunk the areas of densification where and when I find them. I sometimes joke that I’m a “body plumber,” but the analogy holds.

The founder of structural integration, Ida Rolf, used to teach that tissue changed due to sustained heat, pressure, and friction to create a gel-sol response in the ground substance of the extracellular matrix, thus “melting the tissue.” In her last years, she changed her thinking about this but did not yet have the science to propose a different hypothesis.

We do now, but our patients and clients have to do their part too. We can free up those densifications so they can move more freely and with less pain, but they have to incorporate more movement throughout their day when they are away from our treatment tables. This recapitulates the cellular process of improved slide and glide and has the potential to expand it.

Use it or lose it is a biological reality. 

Note

1. This is not unusual. It’s how most science and new information works: something is discovered, gets written about, and gets written about again and again until the discovery takes hold in the world. Rock stars of science like Einstein’s Theory of Relativity or gene editing are the exceptions. For comparison’s sake, the enteric nervous system, the gut brain, or Shen Ch’ue, the “mind palace” in Chinese medicine, was first mapped out and published in 1907, further reinforced by a landmark nervous system textbook in 1921, but didn’t enter the popular consciousness until the 1990s. 

Resources 

Menon, R. G. et al. “T1Р-Mapping for Musculoskeletal Pain Diagnosis: Case Series of Variation of Water Bound Glycosaminoglycans Quantification Before and After Fascial Manipulation in Subjects with Elbow Pain.” International Journal of Environmental Research and Public Health 17, no. 3 (January 2020): 708. https://pubmed.ncbi.nlm.nih.gov/31979044.

Pratt, R. L. “Hyaluronan and the Fascial Frontier.” International Journal of Molecular Science 22, no. 13 (June 2021): 6845. https://pubmed.ncbi.nlm.nih.gov/34202183.

Roman, M. et al. “Mathematical Analysis of the Flow of Hyaluronic Acid Around Fascia During Manual Therapy Motions.” Journal of the American Osteopath Association 113, no. 8 (August 2013): 600–10. https://pubmed.ncbi.nlm.nih.gov/23918911.

Stecco, A. et al. “Densification: Hyaluronan Aggregation in Different Human Organs.” Bioengineering 9, no. 4 (April 2022): 159. https://mdpi.com/2306-5354/9/4/159.

Stecco, C. et al. “Hyaluronan Within Fascia in the Etiology of Myofascial Pain.” Surgical and Radiologic Anatomy 33, no. 10 (December 2011): 891–6. https://pubmed.ncbi.nlm.nih.gov/21964857.

Stecco, C. et al. “The Fasciacytes: A New Cell Devoted to Fascial Gliding Regulation.” Clinical Anatomy 31, no. 5 (July 2018): 667–76. https://pubmed.ncbi.nlm.nih.gov/29575206.