Malcolm I V Jayson, Professor of Rheumatology from the Manchester and Salford Back Pain Centre, writes that:

Degenerative changes in the spine may consist of bony enlargement and ostephyte encroachment either into the spinal canal, causing central stenosis, or into the intervertebral foramen, leading to foraminal stenosis . . . radiographic correlation with symptoms is poor. Muscle spasm is often identified as a cause of back pain.

Abnormalities of muscle tone can occur secondary to neurological damage and may in turn contribute to chronicity. On the other hand, patients with chronic back pain have paraspinal muscle wasting that is contrary to expectations.

Mechanical problems are therefore difficult to identify as the sole source of the back trouble. Secondary processes are likely to be associated with spinal damage and the development of chronic pain. Degenerative change in the spine is associated with obstruction of the epidural veins, fibrosis in and around the nerve roots, and atrophy of the neurones within the nerve roots. Venous obstruction may lead to perineural anoxia and the development of perineural fibrosis and neuronal atrophy. Distended veins in the epidural plexus, damage to the pain receptors in the nerve root sheaths, and loss of neurones with a deafferentiation syndrome could all lead to chronic pain.

Many patients complain of severe disability and widespread pain. They may have tenderness over their back and global motor and sensory problems in their lower limbs.

(Talk Back, National Back Pain Association, Winter '94/'95, p4)