Lower back spasms, like any muscle spasm, is usually the body's reaction to injury.
It can also be caused by mineral imbalances such as that found in calcium and magnesium. These minerals are needed for proper muscle function and when there exists mineral imbalances or deficiencies muscles will be unable to do their balancing act between being too flaccid or too toned.
There are certain neurological diseases or injuries that can also cause a muscle to spasm such as is found in cerebral palsy or torticollis.
Of course there are organ diseases that may cause muscle spasms (parathyroid disease, kidney disease).
Other causes of muscle spasm are:
When lower back spasms are due to injury there is muscle tissue that has been traumatized by strain. Any time your muscle tissue is strained there is tearing. This tearing is usually microscopic or minor. Or it can occur in the form of macro-trauma as what happens with severe rotator cuff tears.
In either case there are chemicals released by the injured tissue that sets off a spasm-inflammation-pain process or cycle. This process, including spasm is the body's way of healing.
The muscle spasm acts as a splinting mechanism which presents further motion thereby reducing the risk of further damage.
When you artificially relax spasm you will have a false sense of healing and you may unwisely continue to use the injured muscle. This could cause further tearing resulting in a greater risk of permanent injury, extensive scarring, chronic pain and disability.
Essentially, lower back spasms is nature's way of splinting or "casting" the injured area. Thus allowing the body's normal healing process to take place without suffering further damage.
When you cover the pain with pain killers, slow or attempt to stop the inflammation process with anti-inflammatories and reduce muscle spasm with muscle relaxers you interfere with the normal natural healing power of the body and end up with more damage, more dysfunctional muscles, more extensive scar tissue and ultimately chronic lower back pain and disability.
The goal is to allow normal healing and at the same time control inflammation. Excessive inflammation causes excessive pain which then causes excessive muscle spasm.
When muscle relaxers and pain killers, as well as anti-inflammatory drugs are taken, you feel better. But, at the expense of feeling better you risk further damage because you no longer have back pain and spasm to prevent you from engaging in further damaging activities.
This is seen in pro-football players that had been given anti-inflammatory drugs (cortisone) and other drugs to help them feel better sooner and resume play.
The long-term result is what these retired football players are now facing...
...chronic degenerative joints (arthritis) and excruciating daily severe pain and a life of disability.
If you have spasm due to a calcium/magnesium imbalance you may have spasm or cramping in your lower back and most likely in your calves and feet. These are often referred to as "charlie horses". They usually occur during the night and are quite painful for several seconds.
You may also suffer with chronic low-grade chronic spasm or hypertonicity in your low back due to a calcium/magnesium imbalance. This is most often seen with those that consume red meat, dairy, soda and coffee.
These foods will create a phosphorous excess and or a diuretic effect. With phosphorous excess the kidney will remove the excess phosphorous from your body. However, in removing this excess phosphorous the kidneys will also remove calcium. So now you have created a calcium deficiency or imbalance.
Muscles need calcium for normal function. When there are imbalances the muscles will most likely be prone to cramping or spasms. The solution to this problem is to reduce intake of those foods and/or use calcium/magnesium supplements, or consume more calcium/magnesium rich foods such as dark green vegetables.
Proper treatment of lower back spasms, including rehabilitation of the injured muscles and attention to your nutrition, and taking steps to prevent further injury is essential for a full recovery. Failure to perform these necessary actions and you risk unnecessary chronic lower back pain.