Untitled Page

Figure 17. Lifting injuries are a common cause of disc problems in both the neck and the low back.

Now that you have a basic understanding of the terminology for describing disc injuries and related conditions, let's talk about how these problems occur. Most disc injuries, regardless of what part of the spine is involved, occur from some combination of compression of the spine, forward bending of the spine, and/or rotation of the spine.

Compression of the spine occurs whenever you are upright in gravity (in other words, when you are standing or sitting), and/or when you are lifting against resistance (some weight lifting machines, such as leg presses, can cause compression of the spine even if you are lying down).

The discs are designed to handle quite a bit of compression coming straight down the spine, so compression alone rarely causes disc injuries. Although lifting a very heavy weight or falling from high up could produce a disc problem, compression becomes much more of a factor when it is combined with either forward bending or rotation of the spine.

Forward bending causes uneven compression of the discs, compressing more to the front and shifting more inside pressure to the back of the disc. Repeated forward bending or a single incident of forward bending combined with significant compression or rotation can overstretch or tear the back portion of the disc wall (the annulus) and start a bulge or rupture. As an analogy, imagine squeezing one side of a jelly donut with your fingers and the gel pushing out the other side.

Although excessive backward bending could potentially cause damage to the front of the disc wall, particularly when combined with a lot of compression, this is a much less common occurrence simply because most people do a lot more forward bending than backward bending. Even if a disc does bulge forward, it usually does not produce bad symptoms because there are no major nerves in this area. Unfortunately, disc bulges or ruptures toward the back of the spine that result from forward bending have a high potential to compress the spinal cord and/or the spinal nerves.

Rotation of the spine is usually not problematic when one is lying down and there is no significant compression of the spine. Combined with significant compression though (such as when lifting or carrying something heavy), rotation can do some major damage to the retaining wall of the disc and cause it to be damaged, resulting in a disc bulge or rupture.

Now that you understand the main movements and positions that can damage discs, let's talk about the onset of disc problems.

There are two main ways that disc problems begin: macrotrauma and microtrauma.

Macrotrauma (or "big" trauma) consists of major damage that occurs all at once. This would include falls, car accidents, lifting something too heavy or the wrong way, etc.. With macrotrauma, the body is simply overloaded all at once and the disc is damaged by the overload. The outer wall of the disc may be overstretched or torn, and the result is a disc bulge or even a rupture. In these cases, there is usually severe inflammation that follows the trauma within 24 to 36 hours, continuing for days or weeks thereafter, and the swelling from this inflammation may contribute to the pressure on nerves and the accompanying pain and other symptoms.

The other source of disc injuries is microtrauma. Microtrauma is the accumulation of many small, unnoticeable injuries over time that eventually weaken the disc wall sufficiently for it to bulge far enough or rupture and begin producing symptoms. The majority of disc injuries probably arise at least partially from microtrauma.

Even many disc injuries that are blamed on lifting something too heavy or the wrong way probably actually started as a gradual weakening of the disc over time from microtrauma. Common sources of microtrauma to the disc include excessive sitting (particularly in a slouched or unsupported position), improper bending and lifting, high impact activities (such as running, jumping, off-road cycling, and any other activity that "jars" the body repeatedly). In the case of the neck, microtrauma can occur from working with the head bent down a lot, or even from sleeping with the head propped up on multiple pillows.
Illustrations showing common causes of microtrauma are shown in the full version of this book.

Ironically, one common source of microtrauma to the back is performing certain weightlifting exercises intended to strengthen the back (such as straight-legged deadlifts and "good mornings" where one bends forward at the waist with a barbell resting on the shoulders). It should be remembered that any forward bending of the spine while sitting or standing puts a lot of stress on the discs, particularly in the low back.

Unlike muscles that get stronger with repeated stress, discs get weaker the more you stress them.

Most people have heard that they should "lift with their legs". This is true, but it is possible to primarily use your legs to bend down and lift things and yet still put your back in a position where there is a high risk of injury. Many times people will still bend forward at the waist even though they are bending and lifting with their legs. While it is not always possible to do so, a safer way to lift is to remember to stick out your rear-end when you bend and lift. This position helps to maintain the normal front to back curve in the low back, which helps protect the discs from injury. It also helps to hold anything you are carrying as close to your body as possible, as this reduces the leverage the load you are carrying has on your spine. Finally, if you are moving things from one spot to another, it is best to turn your whole body as a unit by moving your feet, rather than twisting at the waist.

Illustrations of lifting techniques are shown in the full version of this book.