Low Back Segmental Stiffness
As children we have the great gift of a mobile, strong, well designed and painless spine and it is unusual for stiffness to be an issue as the lumbar spine has evolved to do the job of weight bearing and providing movement. Intervertebral discs separate the spinal vertebrae, allowing more movement in areas where they are thicker and also coping with variable loads. The posterior spinal facet joints limit and control segmental movement, preventing the spine from displacing inappropriately under the shear forces. Strong, balanced and coordinated muscle actions complete the picture.
An acute episode of low back pain inhibits the core stabilising muscles from working well and can cause wasting of them with time. Segmental loss of stability control can make the occurrence of further low back pain episodes at the same level more likely. As time and injuries change the spine, degenerative changes can occur in the facet joints and discs, leading to segmental stiffness and chronic back pain. The force of gravity pushes fluid from the discs by compression and is opposed by a chemical absorption of fluid which is more powerful in lying.
Discs will narrow and lose part of their hydration under the forces of compression which occur in normal life, the disc becoming stiffer and narrower. X-rays can show up this narrowing when it reaches a certain level, but many discs will be troublesome long before this stage. The intervertebral disc and the two vertebrae each side of it are referred to as a vertebral segment and an abnormal stiff segment will move in such a way as to impose inappropriate levels of load upon structures not adapted to take them. The stiffness of individual spinal segments can be felt by a physiotherapist palpating the spine.
Protective muscle spasms are common after an injury and this splints the affected area and allows the process of inflammation and healing to get started. With the gradual resolution of the injury and its pain reduction the amount of back spasms normally lessens and slowly normal movements begin to be apparent again. But muscles can remain in muscle spasm in some cases, leading to a stiffened and shortened group of spinal structures which, by this adaptive shortening, leads to the production of shortened and abnormal spinal joints, ligaments and muscles.
Segmental stiffness can also be contributed to by sitting too much with its increased spinal compression forcing fluid from the discs. Avoiding flexion for many of us has led to a loss of this useful and disc-maintaining movement which increases fluid throughput to the discs and keeps them healthy. Other contributors are maintaining abnormal postures and weakness of the abdominal muscle group.
Sarah Key, a physiotherapist who is well known in the UK, has produced the Sarah Key's Back Sufferers Bible, a book in which she sets out her views of what is going on in this most common of musculoskeletal syndromes. She does acknowledge that it is hard to bring solid evidence for many of her interpretations but seems to have many good and practical therapy ideas to approach the back pain problem with. She covers the main syndromes which typically occur, giving treatment routines for self management of each one, all of which I have found very useful for my own lower back pain. Now I have something I can do about it rather than accept it as a fact of life.