Joint Knowledge: The Spine

Your spine may be the second most important part of your anatomy, second only to the brain. The spine provides structure to our bodies, giving them shape and allowing them to withstand the forces of gravity. This is not the spine’s only job; it also protects the spinal cord, which connects the brain to the rest of our body.

Clearly, the spine has an essential role in maintaining our health and helping us to stay active, so let’s learn more about what precisely the spine is as well as some of the key joints involved.

 

What is the spine?

The spine is the general term given to the bones and ligaments that join to protect the spinal cord. Other terms people use interchangeably are the backbone, vertebral column, or spinal column. It is composed of 24 total vertebrae that are stacked on top of each other like bricks.

The cervical spine, or neck, is composed of the top seven vertebrae that join the skull to the thoracic spine. The thoracic spine is composed of 12 vertebrae, each with an associated rib, forming the rib cage. The bottom five vertebrae are known as the lumbar spine and form what most people consider the ‘low back.’

An individual vertebra has two main parts: a front and a back. The front portion is the ‘vertebral body,’ which is the square brick-like structure, which does most of the weight-bearing. In the middle is a hole that the spinal cord travels through. The back of the vertebral body is made up of a bony roof over the spinal cord known as the lamina, as well as hinge joints known as ‘facet joints.’ At the very back of a vertebra, you’ll find a bony protrusion known as the ‘spinous process.’ You can find it by running your fingers along the middle of your neck or back.

 

Intervertebral Discs

If we were to think of the brick analogy we discussed earlier, the bony vertebra is the brick, and the intervertebral disc

is the mortar. There is an intervertebral disc (IVD) between each vertebra (except for the first two cervical vertebrae), and the purpose of the disc is to act as a shock absorber.

The IVD is made up of collagen, which is the main protein found in ligaments. It is composed of two major parts: the nucleus pulposus and the annulus fibrosus.

The middle of the nucleus pulposus has a spongy consistency of crabmeat. It is surrounded by concentric circles of annulus fibrosus, which is dense and rubbery, similar to a pencil eraser in stiffness.

This structure allows the IVD to be a shock absorber while maintaining its shape and not allowing too much motion.

 

Facet Joints

The facet joints are the hinge-like joints in the back portion of the vertebra. Each facet joint is formed by two different portions of bone – one from the bottom facet of the top vertebra and another from the top facet of the bottom vertebra. There is also a left and right facet for each vertebra.

If you were to look at the vertebra from the side, the facet joints would look like shingles interlocking with each other. Each facet joint is filled with a small amount of synovial fluid and surrounded by a joint capsule, just like other synovial joints throughout the body. The facet joints are integral in allowing you to bend forward or backward.

 

Spine Health

As we age, all our joints will undergo some degree of degeneration. This spine is no exception, and for many people, it is one of the first joints to show the signs of aging. There are no specific genetic risk factors for developing arthritis in your spinal joints, but some research has found that people with a family history of spine issues may be at a higher risk^1,2. Below are some tips to ensure your spine stays healthy for years to come:

• Watch your weight. The spine is responsible for resisting the effects of gravity on your body. Simply put, the heavier you are, the more work your spine must do. One of the most straightforward steps you can take to safeguard your spine health is simply to try and maintain as close to your ideal body weight as possible.
• Don’t smoke! Several studies have established the negative effects for your general health, but did you know smoking is terrible for your back³? It can impair the normal process of healing that helps the spine rejuvenate itself, leading to premature arthritis. If you smoke, you should consider quitting, and if you don’t – don’t start!
• Be cautious. Often, it’s not what we do but how we do it. Lifting heavy weights isn’t inherently bad for you; in fact, it can improve your bone health significantly. What’s important is to be conscious of how you’re using your back. Lifting with your legs, squatting down to an object to pick it up, and lifting with help are all important steps you can take to shield your spine from excessive forces that could damage the spine joints.

 

Conclusion

Your spine is important to your overall health and is responsible for doing a significant amount of work every day. The main joints in your spine, the intervertebral disc, and the facet joints are essential to helping your spine maintain your posture and preventing injury to your spinal cord or nerves. Be sure to stay spine health conscious – not smoking and watching your weight are two straightforward steps you can take to improve your spine health, today!

 

References

1. Patel AA, Spiker WR, Daubs M, Brodke D, Cannon-Albright LA. Evidence for an inherited predisposition to lumbar disc disease. J Bone Jt Surg – Ser A. 2011;93(3):225-229.
2. Simmons ED, Guntupalli M, Kowalski JM, Braun F, Seidel T. Familial predisposition for degenerative disc disease. A case-control study. Spine (Phila Pa 1976). 1996;21(13):1527-1529.
3. Kwon JW, Ha JW, Lee TS, Moon SH, Lee HM, Park Y. Comparison of the prevalence of low back pain and related spinal diseases among smokers and nonsmokers: Using Korean national health insurance database. CiOS Clin Orthop Surg. 2020;12(2):200-208.