Yes, but the stiffer side is not the same for every muscle. A 2025 shear wave elastography study of adolescent idiopathic scoliosis found the erector spinae measured stiffer on the convex side, while the psoas major and quadratus lumborum measured stiffer on the concave side. The size of that gap tracked with the Cobb angle.
What Did the Elastography Study Actually Find?
Different paraspinal muscles went stiff on opposite sides of the same curve. A 2025 study in Spine Deformity used shear wave elastography to measure paraspinal muscles in adolescents with idiopathic scoliosis. The erector spinae showed higher stiffness on the convex side. The psoas major and quadratus lumborum showed higher stiffness on the concave side. The difference between sides was larger in patients with larger Cobb angles. That pattern matters clinically because it means a single measurement point on one muscle can give you the opposite impression of the trunk as a whole.
Is Muscle Asymmetry a Consequence of the Curve or Part of It?
The research points both ways, and the direction is not settled. A 2026 study in the Journal of Clinical Medicine used CT to show paraspinal muscle asymmetry scaling with deformity severity, which is consistent with loading. But separate work on neurogenic changes in paraspinal muscle reports fiber-type differences between sides, which suggests the muscle is not simply responding to geometry. A 2025 paper in Clinical Orthopaedics and Related Research found the timing of paraspinal muscle activation also differs in adolescents with scoliosis compared to those with a symmetrical spine. Asymmetry may reflect both mechanical and neuromuscular factors at once.
How Much Asymmetry Is Normal in a Patient Without Scoliosis?
Roughly 10 to 14 percent, based on healthy-adult reference data. A 2025 myotonometry pilot study reported average bilateral asymmetry in that range in healthy young adults. That is the baseline you are measuring against. A small left-right gap is ordinary. The finding worth acting on is a large gap, or a gap that moves in the wrong direction across a course of care.
| Muscle | Stiffer side in the 2025 scoliosis study | What that means for measurement |
|---|---|---|
| Erector spinae | Convex | Most accessible superficial site, easiest to re-measure |
| Quadratus lumborum | Concave | Opposite direction, so do not assume one stiff side |
| Psoas major | Concave | Deep, not reachable with a handheld surface device |
| Healthy comparison | Neither | Typical bilateral asymmetry is about 10 to 14% |
What Can You Do With This in Practice?
Measure both sides at fixed points and watch the gap, not the number. A single reading tells you little on its own. The same two points measured at baseline and at each re-examination tell you whether the side-to-side difference is widening, narrowing, or holding. That is something you can show a patient or a parent who wants to know whether anything is changing between X-rays. Two limits are worth saying out loud. A surface stiffness reading cannot reach the psoas, and a reading does not diagnose scoliosis or estimate a Cobb angle.
Survey data: In a 2026 survey of 455 patients who stopped chiropractic care, 58% cited perception-based reasons: 36% felt no progress, and 22% felt better and stopped. Neither group was told their stiffness was still elevated.
Frequently Asked Questions
Which side is stiffer in a scoliotic curve?
It depends on the muscle. In a 2025 shear wave elastography study of adolescent idiopathic scoliosis, the erector spinae measured stiffer on the convex side, while the psoas major and quadratus lumborum measured stiffer on the concave side. So there is no single stiff side across the whole trunk.
Does more asymmetry mean a worse curve?
The 2025 elastography study reported that the size of the side-to-side stiffness difference correlated with the Cobb angle, so larger curves showed larger asymmetry. That is an association within one cohort, not a way to estimate a curve angle from a stiffness reading.
How much left-right stiffness difference is normal?
In healthy adults, a 2025 myotonometry pilot study found average bilateral asymmetry of roughly 10 to 14 percent. A modest left-right gap on its own is ordinary physiology, so asymmetry only becomes interesting when it is large or when it changes over time.
Can a stiffness reading diagnose scoliosis?
No. Scoliosis is diagnosed radiographically by Cobb angle. A stiffness reading describes how the soft tissue on each side responds to a mechanical impulse, which may reflect a muscular pattern around a curve but is not a substitute for imaging.
Does asymmetric stiffness cause the curve, or does the curve cause it?
The direction is not settled. Research on paraspinal muscle asymmetry in adolescent idiopathic scoliosis points to both mechanical loading and neurogenic changes in the muscle, so asymmetry may be a consequence, a contributor, or both.
Does a stiffer side mean that side hurts more?
Not necessarily. Stiffness and pain are independent measures and frequently disagree. A patient can report symptoms on the side that measures less stiff, which is why a stiffness reading should be recorded alongside pain rather than in place of it.
What should a practitioner do with an asymmetric reading?
Record both sides at baseline and re-measure at the same points at each re-examination. The useful signal is not the single number but whether the gap between sides widens, narrows, or holds steady across a course of care.
One approach is to add a second channel of objective data alongside subjective pain reports. Options include soft tissue stiffness measurement (such as MuscleMap), range-of-motion testing, and posture analysis. Each gives you something concrete to show the patient rather than asking them to take your word for it.