Spinal Curves

Lumbar and Cervical Curves - Why Do They Matter?

The sacrum bone wedged between the 2 hip bones in back.
The spinal column sits on top of the sacral base, which is the top of the triangular sacrum bone.. Mark Strozier

Did you know that the spine is not designed to be straight? It's true. Based on its position relative to a number of other bones in your body, the spine has to take pressure, weight and force from structures that, by comparison, tend to be heavier and bulkier. As if that weren't challenging enough, as part of its job, the spine must help keep your whole body balanced in both stillness and in movement.

It accomplishes this, in part, by means of curves in its architecture.


The spinal column is composed of 33 vertebrae. Most of the column sits on, and is therefore supported by, the "sacral base." The sacral base is the top surface of the sacrum bone, which is a triangular bone wedged in between your two hip bones in back. The sacrum bone naturally angles forward a bit, which means that right at the bio-mechanical foundation, the stage is set for the presence of spinal curves - all the way up the column.

Below the sacrum bone is your coccyx bone, aka the tail bone.

And while you may think of the spinal column as your backbone, in reality it is located in the middle of your body - extending from the center of your skull through your trunk to your sacral base. (You can also understand this the other way around - i.e. the spinal column extending from the sacral base up through the trunk to your skull.)

The spinal column houses the spinal cord, which is a key structure of the central nervous system. The spinal cord runs through a hollowing in the center of the stack of spinal bones (also known as vertebrae) that make up the spinal column.

An upright position of the spine - as when you sit up or stand up - is technically called "posture" and/or "static spine".

It is from this erect "posture" that anatomists make measurements and create references used for determining what is normal and healthy about your musculoskeletal alignment, and what needs work.


The spine is divided into the following regions: Cervical (neck), which is composed of 7 vertebrae, thoracic (mid and upper back), composed of 12 vertebrae, lumbar (low back), composed of 5 (and in some people, 6) vertebrae, the sacral (sacrum bone, which is 1 bone made of several bones fused together evolutionarily), and coccyx (tail bone, made up of 3 fused bones.)

Related:  Thoracic Spine Pain

These regions correspond to your spinal curves. Generally only the cervical, thoracic and lumbar curves are talked about to any great extent, especially when the communication is given by doctors and physical therapists to non-medical people (i.e. their patients.) Limiting the talk about spinal curves to the cervical, thoracic and lumbar is also a common practice in the media.

Taken as a whole, the curves in an adult spine make an "S" shape when you look at the body from the side.

From the side view, some of the curves go forward toward the front of your body and others go backward. The direction of each curve (i.e. forward or back) alternates from curve to curve; this alternation helps you maintain body posture as well as negotiate challenges to your balance.

In fact, the curves are actually classified according to the direction into which they go when viewing the whole spine (body) from the side. The term that describes the neck and low back curves is lordosis. The term for the thoracic and sacral curves is kyphosis. (You've probably heard of kyphosis as a posture problem. But in reality, kyphosis is the general name for a type of curve, and when there's too much of it - regardless of the specific region in which it is located - it becomes a label for a problem or medical diagnosis. The same is true for "lordosis.")

Called the primary curve, only the kyphotic curves (thoracic and sacral - as one big "C" shape) are present when you are born. The others develop as you acquire the ability to lift your head (cervical curve) and learn to walk (lumbar curve.)  These are considered secondary curves because you develop them after you're born.


The transition areas between the spinal curves are called junctions. For example, the cervicothoracic junction is the area between your 7th (and last) cervical vertebra and your 1st thoracic vertebra. The thoracolumbar junction is the area of transition between the thoracic spine and your lumbar spine. Because the junctions involve a change of direction between one curve and the next, they are sometimes more vulnerable to wear and tear and other types of injuries.


Calliet, R. Low Back Pain Syndrome. 5th ed. Pain Series. F.A. Davis. Philadelphia.

Wang VY1, Chou D. The cervicothoracic junction. Neurosurg Clin N Am. 2007 Apr;18(2):365-71. http://www.ncbi.nlm.nih.gov/pubmed/17556139

Continue Reading