The complex muscular patterns involved in idiopathic scoliosis
Our spine can flex (bend) in all directions: forward, backward, and to each side. When we bend in any direction, we can rotate our spine to either side as well. Since we have 24 articulating (moving) vertebrae in our cervical, thoracic, and lumbar spine, and many different muscles that control the movement of our vertebrae, we can develop varied, unique patterns of spinal flexion and rotation.
Scoliosis is never as simple as a single sideways bend or curve in the spine. We always compensate or balance ourselves out by developing other muscular patterns, like rotating to one side, arching our back, or rounding forward.
Let’s talk about some of the most important muscles involved in scoliosis:
The biggest, strongest muscles in our core that flex our spine laterally are our internal and external obliques. Our obliques also rotate our spine, so any chronic tension in our obliques will likely create both a lateral curve and some degree of rotation.
The erector spinae group of muscles travels from the base of the skull and cervical vertebrae all the way down to the pelvis, attaching to each vertebrae and rib. This group of muscles both laterally flexes the spine and extends it, meaning that it arches the back. So, chronic tension in these muscles can create both scoliosis and hyperlordosis, or an exaggerated arching of the lower back.
The intertransversarii are small, short muscles that connect each individual vertebrae to the vertebrae above and below it in the cervical and lumbar portions of the spine. These little muscles laterally flex the cervical and lumbar spine. Since they are the deepest muscles in the neck and lower back, they are nearly impossible to touch or sense internally.
We think of the quadratus lumborum (QL) as a lower back muscle, but technically, it’s our deepest abdominal muscle. The QL attaches our lowest rib to the top of our pelvis, and connects to our first through fourth lumbar vertebrae. This strong muscle laterally flexes our spine to either side, laterally tilts our pelvis (hikes our hips up one at a time), and helps to extend our spine. So, chronic tension in the QL not only contributes to lumbar scoliosis, but also to functional leg length discrepancy and hyperlordosis.
The latissimus dorsi is the broadest muscle of the back, spanning from the lumbar and lower half of the thoracic spine all the way to the upper arm just below the shoulder joint. The latissumus dorsi participates in many actions: extending, adducting, and medially rotating the shoulder, laterally flexing the spine, extending the spine, and even tilting the pelvis forward or to the side.
The transversospinalis group of muscles are small muscles in between each vertebrae, similar to the intertransversarii. But this group of muscles rotates and extends the spine, contributing to both scoliosis and hyperlordosis.
The most important thing to take away from this discussion is the fact that the muscular patterns involved in scoliosis can be very complex. All of the muscles in the core of the body, including some we haven’t mentioned, will be involved in the lateral flexion, rotation, and extension or forward flexion of the spine, as well as in the compensatory patterns we develop in order to balance ourselves out.
The result of so many multi-functional muscles being involved is that idiopathic scoliosis typically involves lateral flexion to one or both sides, rotation to one or both sides, and either or both extension and forward flexion. These turns and twists can occur at various parts of the spine, creating patterns of spinal curvature as unique as we are.
In the next section, we’ll talk about how and why we develop these complex patterns of muscular contraction.
And watch this video to learn how chronic muscle contraction pulls the spine into a curve.