[Biomechanics, Tensegrity & Meridian Concepts 02] How Fascial Tension and Muscle Imbalances May Influence Spinal Rotation in Scoliosis

Learn how paraspinal muscle imbalance, fascial tension, and myofascial force transmission may influence spinal rotation in scoliosis, and why these factors should be considered within a three-dimensional biomechanical assessment.

Introduction

Scoliosis is more than a sideways curvature of the spine. It is a three-dimensional spinal deformity involving changes in the coronal plane, sagittal alignment, and axial rotation of the vertebrae. On a standing X-ray, scoliosis may appear primarily as a lateral curve, but the actual deformity can also involve vertebral rotation and changes in the shape and balance of the trunk. [1]

This three-dimensional nature helps explain why two people with similar Cobb angles can have noticeably different postures, rib prominence, shoulder asymmetry, pelvic alignment, or movement patterns.

One factor that has attracted increasing interest is the relationship between the spine and the surrounding muscles, fascia, and neuromuscular system. Paraspinal muscles do not simply support the spine. They continuously respond to spinal position, movement, loading, and changes in mechanical demand.

Research has identified differences in paraspinal muscle characteristics and activation between the convex and concave sides of scoliotic curves. However, an important question remains: Are these muscular differences a cause of spinal deformity, a consequence of it, or part of a continuing feedback loop? Current evidence does not support a simple answer. [2][3]

Understanding this relationship can nevertheless provide a useful biomechanical perspective on why spinal rotation may be accompanied by asymmetric muscle activity and altered soft-tissue tension.

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What Does Spinal Rotation Mean in Scoliosis?

A normal spine is not perfectly flat in three dimensions. It has physiological curves in the sagittal plane and is capable of rotation around its longitudinal axis.

In scoliosis, however, abnormal rotation can occur together with the lateral curvature.

For example, a thoracic curve may be accompanied by:

• Rotation of the vertebral bodies
• Posterior prominence of the ribs on one side
• Asymmetric scapular position
• Altered thoracic shape
• Unequal paraspinal muscle activity
• Changes in trunk balance

This is why the Adams forward-bend test is useful during clinical assessment. When a patient bends forward, vertebral and rib-cage rotation can become more visible as a rib or lumbar prominence. [1]

Radiographic assessment remains essential because physical appearance alone cannot determine the complete structural characteristics of scoliosis. Standing spinal radiographs are generally used to evaluate the curve and calculate the Cobb angle, while additional imaging may be considered when clinically indicated. [1]

The Cobb angle is important, but it does not fully describe the three-dimensional nature of spinal deformity.

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What Is Muscle Imbalance?

In the context of scoliosis, muscle imbalance generally refers to differences in muscle activity, strength, volume, morphology, endurance, or mechanical behavior between different regions or sides of the body.

The most frequently discussed muscles are the paraspinal muscles, including:

• Multifidus
• Erector spinae
• Longissimus
• Iliocostalis
• Other deep and superficial trunk stabilizers

These muscles contribute to spinal extension, rotation, segmental stabilization, and control of posture.

When the spine becomes asymmetrical, the mechanical demands placed on these muscles may also become asymmetrical.

A systematic review of paraspinal muscle characteristics in adolescent idiopathic scoliosis found low- to very-low-strength evidence for several differences between the convex and concave sides. Findings included differences in muscle fiber characteristics, muscle volume, muscle activity, atrophy, fatty infiltration, and gene expression. Importantly, the authors emphasized that these changes may be either a cause or a consequence of scoliosis. [2]

This distinction is critical.

It would be scientifically inaccurate to conclude that muscle imbalance alone causes idiopathic scoliosis.

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Paraspinal Muscle Asymmetry and Scoliosis

Electromyography (EMG) studies provide another way to examine the relationship between scoliosis and muscle activity.

A 2022 narrative review examined published surface EMG studies of adolescents with idiopathic scoliosis. Across the available measurements, some studies demonstrated greater activation on the convex side, particularly around the curve apex and during certain postural tasks, while many other measurements showed no significant side-to-side difference. [3]

This mixed evidence suggests that neuromuscular asymmetry is not necessarily uniform.

Muscle activation may vary according to:

• Curve location
• Curve magnitude
• Curve pattern
• Task being performed
• Body position
• Skeletal maturity
• Progression status
• Individual neuromuscular strategy

Therefore, a patient should not be assumed to have a simple pattern such as "tight muscles on one side and weak muscles on the other."

The neuromuscular system is considerably more complex.

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How Muscle Activity May Influence Spinal Rotation

Muscles generate forces around the spine.

If these forces are symmetrical, they can contribute to balanced spinal stabilization. If forces become asymmetrical, however, they may contribute to differences in loading or movement across spinal segments.

Consider a simplified example.

If the paraspinal muscles on one side generate greater force than the corresponding muscles on the opposite side, the resulting mechanical moment may influence trunk position or rotation.

However, this should not be interpreted as evidence that asymmetric muscle activity independently creates structural scoliosis.

Instead, a more appropriate model is a dynamic interaction:

Spinal asymmetry → altered mechanical demand → altered muscle activation → altered loading → adaptation of movement and posture

This process may occur in the opposite direction as well:

Altered neuromuscular control → asymmetric loading → changes in spinal movement → potential contribution to asymmetrical posture

The relationship may therefore be bidirectional.

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What Role Does Fascia Play?

Fascia is a connective-tissue system that surrounds, separates, and connects muscles and other anatomical structures.

Rather than viewing each muscle as an isolated unit, modern biomechanical research increasingly examines how mechanical forces can be transmitted between adjacent muscles and connective tissues.

This concept is often described as myofascial force transmission.

A systematic review of intermuscular force transmission found evidence that mechanical tension can be transferred between some anatomically connected muscular structures. However, the authors also emphasized that the functional significance of these connections remains incompletely understood and that differences in experimental methods make direct comparison difficult. [4]

Human in-vivo evidence has also been investigated.

A systematic scoping review identified studies supporting the possibility of myofascial force transmission in humans, but the researchers emphasized substantial heterogeneity and generally limited methodological quality. They therefore supported the existence of such force transmission only cautiously. [5]

This distinction is important for patients.

It is reasonable to say that fascia participates in mechanical force transmission.

It is not currently justified to say that:

"Tight fascia causes scoliosis."

The available evidence does not establish such a direct causal relationship.

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Myofascial Chains and the Spine

Some biomechanical models describe the body as interconnected through longitudinal and functional myofascial pathways.

For example, anatomical and experimental research has investigated connections involving:

• The superficial backline
• Functional muscular chains
• Thoracolumbar fascia
• Paraspinal muscles
• Pelvic and lower-extremity musculature

These relationships provide a possible explanation for why movement or tension in one anatomical region can influence mechanical behavior elsewhere.

For example, the lumbar spine does not function independently of the pelvis and lower limbs. Likewise, thoracic spinal mechanics are influenced by the rib cage, shoulder girdle, abdominal wall, and breathing mechanics.

However, the existence of anatomical continuity does not automatically prove that a particular fascial chain causes scoliosis.

The distinction between anatomical connection, force transmission, and clinical causation must be maintained.

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Fascial Tension and Rotational Forces

Spinal rotation is fundamentally a problem of three-dimensional mechanical balance.

When a vertebral segment rotates, surrounding tissues must accommodate that movement. These tissues include:

• Muscles
• Ligaments
• Fascia
• Intervertebral discs
• Facet joints
• Rib articulations
• Neural and connective tissues

If a scoliotic curve becomes structurally established, soft tissues may adapt to the altered geometry.

Some muscles may operate at shortened or lengthened positions. Others may change their activation strategy to maintain upright posture.

Over time, these adaptations may become part of the individual's habitual movement pattern.