Low back pain remains one of the world’s leading causes of disability, yet in most patients a clear structural cause cannot be identified. This has encouraged researchers to look beyond the vertebrae and intervertebral discs toward other tissues that may contribute to pain and altered movement. One structure receiving increasing attention is the thoracolumbar fascia (TLF)—the broad connective-tissue network covering and connecting the muscles of the lower back.

A systematic review from Robert Schleip and colleagues examined whether the TLF differs between people with nonspecific low back pain and people without pain, and whether these differences can be detected using quantitative ultrasound. The review included 14 studies involving approximately 880 participants, predominantly people with chronic nonspecific low back pain. Researchers assessed fascial thickness and echogenicity, stiffness, shear strain, deformation during movement, and ultrasound measures of tissue microstructure.

The fascia may look different in people with chronic low back pain

The most consistent finding was a difference in TLF morphology.

Several studies found that people with chronic low back pain had a thicker thoracolumbar fascia or thicker perimuscular connective tissue than healthy controls. One early study reported approximately 25% greater connective-tissue thickness, while another found TLF thickness of around 2.27 mm in people with chronic low back pain compared with 1.96 mm in controls.

Changes in echogenicity—the brightness and appearance of the tissue on ultrasound—have also been reported.

These observations suggest that connective tissue in the lumbar region may undergo structural changes in association with persistent low back pain. Importantly, however, ultrasound cannot currently tell us exactly what those changes represent. Increased thickness should not automatically be labelled fibrosis, adhesions or fascial densification. It could potentially relate to tissue organisation, loading history, fluid content, altered movement or other biological processes.

Is the fascia stiffer?

The answer is less straightforward.

Studies using shear-wave elastography have generally reported higher stiffness-related values in people with chronic low back pain. In one study, greater TLF stiffness was also associated with greater pain intensity.

However, another study using strain elastography found the opposite pattern, suggesting greater fascial compliance in participants with low back pain.

These findings are not necessarily contradictory because the techniques measure tissue mechanics differently. Probe pressure, tissue loading, participant position, muscle activation and the anatomical region being measured can all affect the result.

At present, therefore, there is insufficient evidence to classify patients into clinically meaningful categories such as a “stiff fascia” or “loose fascia” phenotype.

Fascial movement may also be altered

Dynamic ultrasound allows researchers to examine how fascial layers move relative to one another during trunk movement.

Some of the most interesting findings involve shear strain and deformation.

In acute low back pain, studies generally found reduced fascial deformation during movements such as trunk extension or lifting. One study reported a striking difference during trunk extension, with substantially less deformation in people experiencing acute low back pain.

Chronic low back pain is more complicated.

An influential earlier study reported approximately 20% less shear strain, supporting the idea that fascial layers may not glide as freely in some people with chronic pain. More recent research, however, has reported increased shear strain under a different movement protocol.

Thus, both increased and reduced fascial movement have been observed.

For therapists, this is an important reminder that fascial movement cannot yet be interpreted simply as “more movement is good” or “less movement is bad.” Pain-related guarding, muscle contraction, movement strategy and measurement technique may all influence the result.

Can manual therapy change the fascia?

A small number of intervention studies suggest that some ultrasound measurements can change following treatment.

Four sessions of Gua Sha therapy were associated with a reduction in measured TLF thickness compared with a hot-pack intervention. A myofascial technique also produced a small immediate decrease in measured fascial thickness, although TLF stiffness itself did not significantly change compared with sham treatment.

By contrast, a single 10-minute massage session did not significantly alter shear-strain measurements.

An eight-week multimodal chiropractic programme also produced variable rather than uniform changes in fascial mobility.

These findings are interesting but remain preliminary. A measurable change on ultrasound does not necessarily mean that pathological tissue has been “released”, that adhesions have been broken down, or that normal fascial function has been restored. The studies remain few, generally small and often involve short follow-up periods.

What does this mean for therapists?

The emerging evidence supports considering the thoracolumbar fascia as one component of the complex system involved in low back pain.

People with nonspecific low back pain may show differences in:

• fascial thickness and ultrasound appearance;
• mechanical stiffness;
• sliding or shear behaviour between fascial layers; and
• deformation of the fascia during movement.

However, these findings are currently group-level research observations rather than diagnostic tests. Quantitative ultrasound measures should still be regarded as candidate imaging biomarkers. No universally accepted thresholds currently exist that allow a clinician to scan a patient’s fascia and determine whether it is pathological.

This is particularly important because fascial behaviour cannot be separated from the muscles beneath it. Muscle contraction, motor control, physical activity, body composition, movement behaviour and pain-related guarding can all alter the mechanical environment of the fascia.

The clinical message

For therapists, perhaps the most useful conclusion is not that “fascia causes back pain,” but that the thoracolumbar fascia appears to participate in the broader biomechanical and sensory system of the lumbar region.

The strongest evidence currently concerns greater TLF or perimuscular connective-tissue thickness in chronic nonspecific low back pain. Evidence for altered stiffness, shear strain and deformation is promising but considerably less consistent.

Manual and movement-based therapies may influence some measurable fascial properties, but evidence that these changes represent a specific therapeutic mechanism remains limited.

The TLF therefore deserves attention—but within a wider clinical assessment that includes pain, movement, muscle function, strength, motor control, activity, psychosocial factors and the patient’s individual presentation.

Rather than treating the fascia as an isolated structure that must be “released”, current evidence supports viewing it as part of an interconnected muscle–fascia–nervous system whose structure and behaviour may change alongside low back pain.