Welcome to your Lumbar Spine
I’ve mused in some of my recent blog posts about how we might view our body as a stack of joints, the importance of variable movement and the cardinal planes, and the concept of “stiffness” (which is really about stability) in our spine. Now I’d like to delve into how the various segments of the spine work together as a functional family to support full body movement.
The individual regions of the spine are the cervical (neck), thoracic (trunk), lumbar (lower back), and the sacral/coccyx (what’s at the base of the spine and intimately related to pelvic function). They are arranged in a series of curves front to back.
The thoracic and sacral segments are called primary curves because they develop in utero. From the side they can be viewed as convex – they curve out behind you.
The cervical and lumbar segments are called secondary curves because they develop after you are born. One of the strongest reflexes we have as human beings is to get our “eyes on the horizon”. Very soon out of the womb, babies begin lifting their heads and building the cervical curve. The lumbar curve is developed as we learn to roll over, sit up, crawl, squat, stand, and ambulate. These curves can be viewed from the side as concave – they curve towards your front body.
One might think I’d start at the top or bottom of the spinal column. But, no, I’d like to first introduce you to your lumbar spine, smack dab in the middle of the thoracic and sacral segments. I’ve told you that I have an interesting relationship with organization, right?
The lumbar segment is a primary load bearing structure. One might say that it’s main job is to bear the weight of the trunk and head, providing stability while allowing adequate mobility for activities of daily living.
Although all elements of the spinal family are important, the lumbar segment is necessary so that the top half of us doesn’t crumble into the bottom half of us. Great gratitude to our lumbar spine and its inherent ability to perform this super important job!
The lumbar spinal segment is comprised of 5 large vertebrae and is concave posteriorly creating what is called a lordotic curve.
It’s a rare week when I don’t hear someone profess that their lumbar spine has too much “lordosis”, or too much curve. Honestly, I rarely see a student or client who is overly lordotic. In fact, I’m much more likely to see posterior pelvic tilt (tucked buttasana). Or I observe forward ribcage posture that often makes it seem like the lumbar might be too curved.
Having and maintaining a lumbar lordosis is crucial for the efficient function of the entire spinal column and the ability to provide a wide variation of movements – rotation, flexion, extension, and side-bending. If you stand and posteriorly tilt your pelvis (tucked buttasana) the ability of the lumbar spine to weight bear and transfer those loads into the legs changes dramatically.
Remember, though, the curve of your lumbar is going to change as you move into and out of “shapes” and activities all day long. When you’re standing still in tadasana, though, see if you can feel your natural lordosis.
Each of the 5 lumbar vertebra has these components:
- The body – weight bearing portion
- Vertebral arch – bony opening for the spinal cord to pass through
- Transverse processes – on the side of the vertebral body, providing tissue attachment sites
- Spinous process – the bony “tail” on the back of the vertebra, also an attachment site. Bend forward and you can palpate the little dinosaur bumps on your lower back
- Facet joints – articular joints that allow movement (read on for more)
The direction of movement for any spinal segment is controlled by the angle of the facet joints on the vertebrae. These are four flattened processes/extensions of the bony surface on the back of each vertebra. Two on the top facing upright (right and left) and two on the bottom facing downward (right and left). The two on the top interconnect with the adjacent vertebra above. The two on the bottom interconnect with the adjacent vertebra below.
These joint surfaces are covered with cartilage so they can “articulate” or move/glide over one another to guide segmental motion between two vertebral segments. Each segment of the spine has facet joints that lie at varying angles to facilitate variable movement.
The phrase “variable movement” will continue to show up in my writing. A lot. As we move around our world our spine changes its shape dependent on what we are doing. We move INTO and OUT OF different positions all the time, but most of us could use doing even more of this thing called “movement”.
But I digress…..
Although the lumbar spine has motion in all three cardinal planes, the facet joints for this segment are parallel to the sagittal plane (sagittal plane explained in this blog post: https://mewithlauriebb.com/variable-movement-is-nutritious-movement-yoga-asana-and-the-cardinal-planes/). This makes flexion-extension pretty accessible for the lumbar spine segment.
No real “normative value” has been established for the degrees of flexion, extension, rotation, and side bending that are possible in the lumbar spine. The definition of “normal” is always tricky because it depends on how range of motion is tested, who is taking those measurements, and who the subject(s) is being measured.
For instance, someone with chronic low back pain might present with very different findings than someone who has never experienced back pain. The devices used to measure the degree of motion are very different. User error, the person taking the measurements, is always possible.
What is true for the human body is that variation is normal, even when collecting data for evidence-based science studies. What we can probably confidently say is that your lumbar spine has considerably more flexion-extension than rotation and side-bending throughout your lifespan.
A few other important components of the lumbar spine, especially in terms of movement, are the discs and ligaments.
The intervertebral discs, nature’s cartilaginous padding between the actual vertebral bones, are really the main connection between the vertebrae. They bear loading forces during axial compression. The axial skeleton is comprised of your skull, ribcage, sternum, and spinal column. So the disc helps to absorb and transfer loads between the vertebrae as you move.
Ligaments connect one bone to the next. The spinal column is comprised of 33 bones. So you can only imagine how many ligaments, small and large, are part of your spinal complex! I won’t take the space to talk about all the ligaments influencing the lumbar spine, but they are there to help maintain stability, limit certain movements, and provide constant disc tension.
It’s also important to acknowledge that the lumbar spine influences and is heavily influenced by the pelvis. There is actually a word for this – lumbopelvic motion or lumbopelvic rhythm.
Let’s consider flexion, extension, side-bending, and rotation in the lumbar segment.
In a seated or standing forward bend, the 5 bones of your lumbar spine will flex in combination with the pelvis (acetabulum) rolling over the femoral heads in hip flexion to get your trunk towards your legs.
The posterior longitudinal ligament (PLL), located over the entire posterior (back) length of the vertebral bodies and discs limits flexion.
It’s important, then, to understand that forward bending is not an isolated act of either lumbar or pelvis and it’s limited not only by what we often talk about as “muscle tightness”, but also bony structure and a protective ligament structure.
Back bending is similar. In upward facing bow (full backbend sometimes called “wheel”) your pelvis rolls backward over the femoral heads as your lumbar spine extends – that is, if your poor little hip flexors allow that pelvis to move! Again, an act of the lumbopelvic rhythm.
And, yes, there is also a ligament that runs the full length of your anterior spine (deep within your body on the front of all the vertebrae) called the anterior longitudinal ligament (ALL). It’s job is to limit spinal extension.
Triangle pose is a side bending posture in the frontal plane. The pelvis laterally flexes and the lumbar spine side bends (and does a couple other things, too). Again, the pelvis and lumbar are dancing together to make this happen and yes another ligament, the intertransverse ligament, resists lateral bending of the trunk.
Now, let’s take a moment and talk about rotation of the lumbar spine. I am practicing using non- “catastrophizing” language these days, but I do regularly warn my students that the lumbar is quite limited in rotation due to the orientation of the facet joints (remember they are more sagitally oriented for flexion-extension)
This is where that lumbopelvic motion really needs to come into play – at least IMO (ok, I’m really proud of myself because I just learned today from a much younger well informed kinesiologist-type person that IMO wasn’t a special training she was posting about, but short for “IN MY OPINION” – can we all just laugh at my lack of social media know how?).
Without catastrophizing, I want to invite you to carefully explore what parts of your spine really turn when you twist. Hint – check your cervical and thoracic spinal segments the next time you do a deep twist. I also want to invite you to explore allowing the pelvis to move with you when you twist because the poor lumbar segment alone just doesn’t have the capacity for much twist and sometimes that means the SI joint in the sacrum/pelvis starts to be asked to do things maybe it might not want to do.
In biomechanics the force acting on the spine causing it to twist is torsion or axial rotation. IMO (there it is again – in my opinion), allowing the pelvis to move with the lumbar spine may help regulate the torque on the tissues in the lumbar spine and the compressive and toque forces being transferred down into the sacrum and SI joints.
Notice how I am allowing the rotation on my left side from the leg through the pelvis into the spine to create the twist to the right rather than holding the pelvis parallel to the ground. This is moving with the lumbar spine rather than asking it to move in a way that it is limited by nature.
Nature has actually provided the iliolumbar ligament, arising from the tip of your last lumbar vertebra’s transverse process (that wing shaped bone on the side) and connecting to the inner lip of your iliac crest (the wing shaped pelvic bone you can palpate horizontal to your belly button), as an assistant to at least two other ligaments to help stabilize your lumbosacral joint (where you fifth lumbar vertebra meets the top of the sacrum segment).
If nature is concerned about stabilizing the base of your lumbar spine as it attaches to your sacrum and influences your SI joint, it seems appropriate that we might be concerned too? It’s good to understand that the lumbar segment is rotationally limited and probably appreciates help from pelvic movement.
This ties back into the idea I started with —- the various segments of the spine work together as a functional family to support a variety of movements.
Nature has provided a lot of stop gap measures so that we can move well and in lots of different directions without easily going past end point range of motion – the way the facet joints align, padding(discs) in between spinal bones, ligaments that prevent too much motion in certain directions, the convex/concave spinal curves, muscles that work with and against one another to help create tensile force.
Again, I find myself face to face with the miraculous reality of the way our body is designed to carry us through this life and allow us so much freedom to move!
Welcome to your lumbar spine. As you step onto your mat this week, as you walk along West Cliff or in the forest, as you sit, stand, bend, twist, ride your bike, surf, or swim, consider this segment of your spine. Listen to it and think about how other parts of your spine and body can help support its full potential of movement.
Here’s to exploring!
