Twelve patients presenting with acute low back pain only and demonstrating intensification of low back pain during passive straight leg raising were investigated with CT or MRI scanning. None of these patients had leg pain. The painful and reduced passive SLR was accompanied by further increase in pain on dorsiflexion of the foot and reduction in pain on knee flexion, findings normally associated with sciatic pain due to acute nerve root compression following disc protrusion.

Imaging demonstrated significant central disc prolapses at L4/5 or L3/4 in all patients. In those who showed unilateral restriction of passive straight leg raising, the scans revealed central disc protrusions with a disposition to the affected side. None of these patients had neurological deficits effecting the leg, bladder bowels.

The clinical presentation, imaging and anatomy of the spinal canal would clearly implicate the anterior dura as being the source of the pain, being compressed by a central disc protrusion. The nerve supply of the anterior dura as opposed to the posterior dura is substantial.

The dura as an origin of acute low back pain has received some but not widespread attention in the medical literature.

The clinical outcome of these patients typically mimicked those who present with acute sciatica. The majority improved spontaneously and only a small proportion continued to have significant pain some months after the onset of symptoms.

Diagnosis of this clinical syndrome, which has not been fully described before, may give some focal point for an explanation of the pain source to the patient and give some lead to further investigations.