Easy Low Back Anatomy
I want you to think of professions that have the most strain on the low back (LB) throughout the day.
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Did you think of an office worker putting in 8+ hours a day?
Probably not, but the amount of stress placed on the LB while sitting is mind-blowing. The average amount of pressure placed on the discs of the low back while sitting can range from 309 lbs in a non-weight bearing position to 408 lbs while leaning forward.
In this final installment of the body breakdown series, we are discussing the anatomy of the lumbar spine aka low back. We will be covering a bit of anatomy, the leading causes of your low back pain while at a desk, some preventative steps you can take, and treatments to seek out.
Anatomy of the low back
For this anatomy section, I wanted to do a quick explanation rather than lose you in all lengthy anatomical details. If you do want to expand your knowledge of anatomy, there are some great resources out there.
Vertebrae
These are the small circular bones that make up your spinal column. There are 33 of them from the base of your skull to your tailbone. The ones you are most likely familiar with are the moveable ones in the neck, mid back, and low back (24 in total). The remaining ones are fused to make up your sacrum and tailbone. They form the foundation for the rest of your body to move and also protect the spinal cord.
Photo Credit Mayfield Clinic
The vertebrae form joints within the spine called facet joints which provide load-bearing and movement properties. These facets are highly innervated, which makes them highly sensitized upon injury. The capsule that surrounds the facet can become injured and irritate the adjacent soft tissue causing pain and spasms within the area.
Discs
The discs act as a cushion between the vertebrae, helping to absorb the stress we put on them. There are three parts to each disc, which I will describe by using an analogy of a delicious jelly doughnut.
Annulus Fibrosus (dough portion)- a fibrous outer part of the disc, which provides the resistance component of the disc
Central nucleus pulposus (jelly)- the gelatinous portion of the disc, which provides the cushion component
Endplates- Cartilage portions between the disc and vertebral body, which are above and below the disc
Muscles of Low Back
Psoas m.- Runs from the lumbar spine to the femur. It aids in stabilizing the spine and flexing the hip. Prolonged sitting causes the Psoas to become tight and overactive as the day progresses.
Multifidus group- Small muscles that run from the lateral aspect of the vertebrae to the spinous process (bony part of the spine). The multifidus group helps stabilize the spine, extend and laterally flex, and contralaterally rotate the spine.
Quadratus Lumborum m. (QL)- Runs from the iliac crest (top of your hip) to the vertebrae of the spine. The QL is a stabilizer of the spine when performing shearing motions and lateral motions. This muscle also extends and laterally flexes the spine as well
Erector Spinae Group (ES)- A group of muscles that extend the spine, which runs along the spine from the cervical spine to the lumbar spine.
Transverse Abdominis (TA)- Deepest muscle of the “Abs group.” Runs from the top of the hips to the fascia of your midline. The TA acts as a corset or like a pair of Spanx for your abdomen. This action helps stabilize the low back.
Sciatic Nerve
You have probably heard of the overly diagnosed and poorly treated condition of Sciatica. Sciatica in its purest definition is pain that radiates down the Sciatic nerve. Sciatica may arise from numerous sources such as muscle compression, disc compression, bony compression, etc.
The Sciatic nerve branches from nerves in the lumbar spine and forms a large nerve that runs down from the back, through the buttocks, and down the back of the leg.
As you can see from the picture the nerve has to travel a significant distance to get to your feet. Hence, its high susceptibility to so much wear/tear and compressive forces. I’m going to go over the whole Sciatic complex in a future post, but I want to provide a quick summary of it.
Wrapping Up
I wanted to break up this low-back post into a couple of segments since the anatomy portion is slightly longer than usual. I’ve also linked an article regarding the best low back exercises (in my opinion) here.
The goal with any pain should be to first educate yourself on the condition, then formulate a plan of attack with the help of a qualified medical provider. I hope this article and the link above will do that for you.