Generic Low Back Pain: An Anatomical Explanation

Low Back Pain (Lumbar)

Acute low back pain has impacted 25% of Americans in the last three months. It is ranked by the CDC as the most common source of pain. If this is you, keep on reading to learn some basic knowledge about your back pain. I will go through some of the most common reasons that people have back pain, and see if I can point you in the right direction.  The spine is complicated, but if you can start to notice patterns about different positions that make things better or worse, it is easier to treat and diagnose. I will introduce the idea of a directional preference and explain several possible anatomical causes of each. There have been many large studies comparing people with back pain and people without, and imaging shows just as many pathoanatomical “problems” in each group. That means we all have some things going on in our spine, but we are not all symptomatic. If you look hard enough at anyone’s spine, you will find something. Throughout the course of life we see changes happen on the outside of our bodies. We see freckles, wrinkles, gray hairs and know that this is the normal process of living. There are changes happening inside our bodies as well, we just don’t see them so when imaging is done it should not be surprising that changes have occurred inside as well. 

Flexion Dysfunction

A flexion dysfunction means that someone has pain when going into lumbar flexion. Flexion is the movement of bending the spine forwards. Some examples of lumbar flexion are more obvious like bending forwards to touch or tie your shoes. Other examples are less obvious but still put the spine into flexion like prolonged sitting and loosing the inward curve of your lower back, or the deepest part of a squat. If you have back pain with any of these types of motions, you probably have a flexion dysfunction. 

Anatomically, flexion puts more pressure on the discs in your back. That pressure can sometimes push on the nerves that exit out of your lumbar spine, and that causes radicular symptoms like sciatica. Nerve symptoms are typically described as numbness, tingling, electric shock feelings, change in sensation, or weakness of certain muscles. Typically these types of symptoms are the result of a flexion dysfunction. 

A common flexion dysfunction is a disc herniation. The analogy I like to use to describe a disc herniation is that the disc is like a jelly donut. When you bend forward (or whenever the spine is in flexion) the “jelly” is pushed towards the skin on your back, which is close to where the nerves are. When you lean backwards you squish the “jelly” towards your belly button side, which is away from the area where the nerves are. 

Medical diagnoses that are flexion dysfunctions include: disc herniation,  lumbar disc degeneration, lumbar radiculopathy, sciatica, sciatic nerve compression, or generalized low back pain. The general rule of thumb is to start with extension based core exercises and temporarily avoid flexion based exercises. The goal is to increase your core strength without irritating your symptoms. Then, by gradually reintroducing your body to flexion, your brain and body will not react as much to the flexion position. Your body is not fragile, it is just not tolerating flexion well right now.

Extension Dysfunction

An extension dysfunction is when someone has pain when going into extension. Extension is when the lower spine curves backwards. We all do extension throughout the day, and examples might be leaning backwards, walking up stairs or uphill, reaching overhead, or even standing for too long. If these movements are painful for you, you probably have an extension dysfunction. 

Anatomically, extension compresses some parts of the spine. There are little joints that are on both sides of the spine called facet joints that can be compressed with extension. The foramen which is the tunnel the nerve root exits from can be compressed in extension. Even the central canal around the spinal cord can be compressed with extension. Extension will also compress the spinous processes in the center of the spine, and the vertebral bodies themselves. 

Some typical medical diagnoses that are extension dysfunctions include spinal stenosis, central stenosis, facet joint pain, spondylolisthesis, or spondylolysis. If you have an extension dysfunction including one of these conditions the general rule of thumb will be to strengthen your core with flexion biased exercises, and gradually introduce extension until you can tolerate it better. Remember, your body is not fragile but it becomes sensitive to certain movement patterns sometimes. 


If you have back pain, try to look out for movement patterns that cause pain or give relief. If you have more pain when leaning forwards, you likely have a flexion dysfunction and will want to strengthen your core with extension biased exercises. If you have pain leaning backwards, you likely have an extension dysfunction and would benefit from strengthening your core with flexion biased exercises. You should never push into pain when exercising with back pain and may need to modify your activity to avoid aggravating your flexion or extension dysfunction. Back pain can get quite complicated, but any healthcare professional will be trying to figure out patterns that make things worse, and things that make you feel better. You will have a head start if you already have a few examples of each. Even though your back may hurt, it is important to know that that exercise has been shown to help. Do some gentle cardio, mobility work, and strengthening to help manage your symptoms. If you would like some ideas of how to help manage your back pain I have created a home rehab program that you can do at your own pace which I use for many of my patients with back pain. Knowing what helps or what hurts will help you change your mindset about your back and equip you with tools to help manage on your own.

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