Joint mechanics of the spine and pelvis: Coupling Side Bending and Rotation.

In clinical practice, we see things like an elevated ilium quite frequently. With the elevated ilium, there is almost always some aspect of pelvic torsion. This word can mean different things, but what I mean is that one ilium will be significantly different than the other in terms of anterior and posterior tilts. One side will be significantly more anteriorly tilted or posterior tilted than the other. There will also frequently be rotations in the pelvis and spine.

Why is this? It really has to do with the mechanics of the spine, sacrum and innominate bones. In movements such as walking and running, the body features a combination of side bending and rotation. As the hip flexes and the leading leg reaches out, that innominate bone will roll into a posterior tilt and it will move anterior. Conversely, the opposite innominate will go into an anterior tilt and shift posterior as it follows the back leg in extension. The sacrum will be part of this complex movement and will 'nod' as it rotates and side bends. This nodding is called nutation and counter-nutation and I will not go into detail here other than noting that that the side bending and rotation are coupled in this movement.

The vertebral joints also couple side bending and rotation. For the lumbar and thoracic spine, these movements are coupled in opposite directions. This means that if a vertebra such as T9 right side bends it will also left rotate. This happens at the individual joint level, but you can see the general global spinal pattern in this video where I am demonstrating an exercise called Windmills.

The Gallbladder Sinew Channel performs Side Bending and Rotation.

There are many channels that are involved with these movements. Even the individual muscles of the transversospinalis group (multifidi, rotatores) contribute to the these coupled movement. The attach from inferior transverse processes and reach up to superior spinous processes, pulling the vertebra they insert on into a side bend to that side and a rotation to the opposite side.

The Gallbladder sinew channel supports this and one of its primary actions is to side bend and rotate the torso. Or it stabilizes to prevent excessive side bending and rotation. Either way, it is intimately involved in this movement pattern. Let's look at some key muscles of this channel.

Consider the abdominal obliques. These muscle both side bend the torso, but also rotate the torso. Another example would be the serratus anterior. This muscle abducts the scapula (this is a type of rotation as it rotates around the ribcage) and it also upwardly rotates the scapula (a side bending movement which medially tilts the scapula). We could continue with other examples such as the piriformis, gluteus maximus, gluteus minimus and gluteus medius; and see that all of these muscles have some action that contributes to rotation and side bending. Sometimes these muscles perform side bending and rotation. Other times they stabilize and prevent side bending and rotation. But, their attachments dictate these movements. Here is another video which highlights a training progression to train the stabilization role of this channel. In these exercises, the starting position is side bending and the channel is then engaged to bring the torso back into alignment against gravity. Again, you will see the coupled movement of side bending and rotation.